Sourdough Oatmeal Fudge Bars

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One of my favorite Starbucks treats was their fudgy oat bars, and I still think about them. Since I love to give everything a sourdough twist, I came up with these Sourdough Oatmeal Fudge Bars. They start with rich brown butter oatmeal cookie layers and are filled with a thick, homemade fudge center. They’re easy to make and every bit as nostalgic as the original.

Tools You’ll Need:

1. 9×9-inch baking pan- to bake your bars. I love this pan 9×9 pan from USA Bakeware.
2. Medium-sized pot- for browning the butter and melting the fudge.
3. Parchment paper- to line your brownie pan for easy removal.
4. Mixing bowl- to mix the cookie dough.
5. Whisk- to mix the brown butter and fudge filling.
6. Spatula- to spread the filling.
7. Digital kitchen scale (optional)– for accurate measuring, especially helpful with sourdough baking. I linked the one I like here.
8. Measuring cups and spoons– for measuring ingredients.
9. Oven safe metal clips (optional)- for holding the parchment down to the pan. I love these metal clips that are heat safe and keep my parchment from sliding around.
10. Hand mixers (optional)- to mix the cookie dough.

Gather Your Ingredients:

1. Unsalted Butter– Creates your brown butter to make that nutty toffee taste. You’ll also use butter in the fudge filling.
2. Egg– Adds richness and moisture to the cookie dough.
3. Sourdough discard– Adds flavor and moisture and is the magic that ferments your dough if you want to ferment the cookie overnight. Can be used fed, past peak, or straight from the fridge.
4. White Granulated Sugar- Helps give the cookie dough that crackly top and crisp edge.
5. Brown Sugar – Adds sweetness and caramel notes to cookie dough.
6. Vanilla Extract – Adds sweet warmth to the bars.
7. Rolled oats- Adds texture and chew to the cookie dough. Do not use steel cut oats.
8. All-purpose flour– Provides structure and lift to the cookie bars.
9. Baking Powder– Helps with lift and rise for the bars.
10. Baking Soda– Creates the perfect spread to the bars.
11. Sea Salt– Enhances overall flavor and sweetness.
12. Semi-Sweet Chips– used to make the chocolate fudge center.
13. Sweetened Condensed Milk- thins the chocolate fudge center. Do not swap!
14. Espresso Powder (optional)– The secret ingredient that really unlocks the flavors of the brown sugar and chocolate. I love this espresso powder from King Arthur linked here.
15. Flaky Sea Salt (optional) – I love adding Maldon sea salt flakes on top of the bars for that extra flair. If you haven’t tried this, I highly suggest it! You can find it link here.

Instructions

Step 1: Brown the Butter

In a medium saucepan, melt the butter over low heat. Continue cooking, stirring frequently, until the butter foams and turns a rich amber color with brown specks at the bottom, emitting a nutty aroma. Remove from heat immediately. This process typically takes about 5-7 minutes.

Once butter is browned, remove the saucepan from heat and transfer the butter to a the mixing bowl to cool for about 10-15 minutes.

Step 2: Prepare the Cookie Dough

Preheat the oven to 350°F (175°C).

Line a 9×9 inch baking pan with parchment paper, and lightly spray with cooking spray.

Add the brown sugar and white sugar to the brown butter, and whisk or cream with hand beaters for 2-3 minutes until butter is well combined with the sugars.

Next you’ll add the egg, sourdough discard, vanilla, and espresso powder to the bowl. Mix on low speed with hand beaters or with a whisk until smooth and well combined. A word of caution, after adding starter don’t beat this on high or for too long or the dough will be puffy.

Toss your rolled oats, all-purpose flour, baking powder, baking soda, salt, and cinnamon in the cookie dough.

Fold the dry ingredients into the wet ingredients just until no dry streaks remain. The dough will be thick! Do not overmix the dough at this stage.

Cover the bowl and transfer to the refrigerator to set while you make the fudge filling. This will help the cookie dough be easier to handle.

Overnight Fermentation Option: If you want to ferment the cookie dough overnight, simply cover the bowl and refrigerate overnight. When you’re ready to make your bars, allow the dough to rest 30 minutes at room temperature so it’s soft and easier to handle.

Step 3: Make the Fudge Filling

In a small saucepan or pot, add the sweetened condensed milk, chocolate chips, and butter. Cook over very low heat just until the chocolate is melted. Whisk constantly, until smooth and glossy.

Remove from the heat and stir in the vanilla and salt.

Allow the fudge filling to cool for 3–5 minutes until slightly thickened.

Step 4: Assemble and Bake

Press about two-thirds of the cookie dough evenly into the prepared pan using lightly damp hands or an offset spatula.

Spread the fudge filling evenly over the cookie layer, making sure you meet the edges.

Pinch off pieces of the remaining cookie dough, flatten them well in your palms, and scatter them over the top. Leave small gaps so some of the chocolate filling remains visible for that classic oatmeal fudge bar look.

If your gaps are too big you can use your fingers to flatten the cookie dough pieces gently to spread them dough.

Bake for roughly 28-30 minutes, or until the edges are golden brown, the cookie topping is lightly browned, and the center is just set with a slight jiggle. Do not overbake or the bars will get dry.

Sprinkle the warm bars with flaky sea salt if desired fresh from the oven.

Cool completely in the pan, then transfer to the refrigerator for at least an hour for the cleanest slices.

You can spray your knife with a little cooking spray to get more clean cuts, I cut this bar in 3 rows vertically and horizontally for 9 even bars.

Enjoy!

Yields 9-12 bars

How to Store:

Room temperature- Keep in an airtight container for 6-7 days. Place a slice of bread in the container to keep them soft.

Freezing- store baked cooled bars in a Ziplock with all of the air removed first. Freeze for up to one month. Allow to thaw to room temperature an enjoy!

FAQ’S

If you loved this recipe, drop a comment and leave a star review and don’t forget to checkout more of my sourdough bar recipes!

Sourdough Bar Recipes:

• Sourdough S’mores Brownies
• Sourdough Cosmic Brownies
• Sourdough Peanut Butter Blondies

Sourdough Oatmeal Fudge Bars

One of my favorite Starbucks treats was their fudgy oat bars, and I still think about them. Since I love to give everything a sourdough twist, I came up with these Sourdough Oatmeal Fudge Bars. They start with rich brown butter oatmeal cookie layers and are filled with a thick, homemade fudge center. They're easy to make and every bit as nostalgic as the original.

5 from 1 vote

Print Recipe Pin Recipe

Prep Time 20 minutes mins

Cook Time 30 minutes mins

Servings 12

Equipment

• 9×9-inch baking pan – to bake your bars. I love this pan 9×9 pan from USA Bakeware.
• Medium sized pot – for browning the butter and melting the fudge.
• Parchment paper – to line your brownie pan for easy removal.
• Mixing Bowl – to mix the cookie dough.
• Whisk – to mix the brown butter and fudge filling.
• Spatula – to spread the filling.
• Digital kitchen scale (optional) – for accurate measuring, especially helpful with sourdough baking. I linked the one I like here.
• Measuring cups and spoons – for measuring ingredients.
• Oven safe metal clips (optional) – for holding the parchment down to the pan. I love these metal clips that are heat safe and keep my parchment from sliding around.
• Hand mixers (optional) – to mix the cookie dough.

Ingredients

  

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Wet Ingredients

• ¾ (170g) cup unsalted butter
• ½ (100g) cup granulated white sugar
• ½ (100g) cup packed brown sugar
• 1 large egg room temperature
• 2 teaspoons vanilla extract
• ⅓ (80g) cup sourdough discard
• ¼ teaspoon espresso powder optional, but recommended

Dry Ingredients:

• 1¼ (145g) cups all-purpose flour
• 1¼ (120g) cups old-fashioned rolled oats
• ½ teaspoon baking soda
• ¼ teaspoon baking powder
• 1 teaspoon fine sea salt
• ¼ teaspoon ground cinnamon

Sourdough Discard Swap:

• 3 (40g) Tbsp all-purpose flour
• 2 (30g) Tbsp whole milk

Chocolate Fudge Filling:

• ⅔ (210g) cup sweetened condensed milk
• 1¼ (210g) cups semisweet chocolate chips
• 2 (28g) tablespoons unsalted butter
• 1 teaspoon vanilla extract
• ½ teaspoon fine sea salt

Garnish:

• flaky sea salt for topping

Instructions

 

Step 1: Brown the Butter

• In a medium saucepan, melt the butter over low heat. Continue cooking, stirring frequently, until the butter foams and turns a rich amber color with brown specks at the bottom, emitting a nutty aroma. Remove from heat immediately. This process typically takes about 5-7 minutes.
  ¾ (170g) cup unsalted butter
• Once butter is browned, remove the saucepan from heat and transfer the butter to a the mixing bowl to cool for about 10-15 minutes.

Step 2: Prepare the Cookie Dough

• Preheat the oven to 350°F (175°C).
• Line a 9×9 inch baking pan with parchment paper, and lightly spray with cooking spray.
• Add the brown sugar and white sugar to the brown butter, and whisk or cream with hand beaters for 2-3 minutes until butter is well combined with the sugars.
  ½ (100g) cup granulated white sugar, ½ (100g) cup packed brown sugar
• Next you’ll add the egg, sourdough discard, vanilla, and espresso powder to the bowl. Mix on low speed with hand beaters or with a whisk until smooth and well combined. A word of caution, after adding starter don’t beat this on high or for too long or the dough will be puffy.
  1 large egg, 2 teaspoons vanilla extract, ⅓ (80g) cup sourdough discard , ¼ teaspoon espresso powder
• Sourdough Discard Swap Option: if you are swapping out the discard, add the milk to the wet ingredients and the additional flour the the dry ingredients below.
  3 (40g) Tbsp all-purpose flour, 2 (30g) Tbsp whole milk
• Toss your rolled oats, all-purpose flour, baking powder, baking soda, salt, and cinnamon in the cookie dough.
  1¼ (145g) cups all-purpose flour, 1¼ (120g) cups old-fashioned rolled oats, ½ teaspoon baking soda, ¼ teaspoon baking powder, 1 teaspoon fine sea salt, ¼ teaspoon ground cinnamon
• Fold the dry ingredients into the wet ingredients just until no dry streaks remain. The dough will be thick! Do not overmix the dough at this stage.
• Cover the bowl and transfer to the refrigerator to set while you make the fudge filling. This will help the cookie dough be easier to handle.
• Overnight Fermentation Option: If you want to ferment the cookie dough overnight, simply cover the bowl and refrigerate overnight. When you're ready to make your bars, allow the dough to rest 30 minutes at room temperature so it's soft and easier to handle.

Step 3: Make the Fudge Filling

• In a small saucepan or pot, add the sweetened condensed milk, chocolate chips, and butter. Cook over very low heat just until the chocolate is melted. Whisk constantly, until smooth and glossy.
  ⅔ (210g) cup sweetened condensed milk, 1¼ (210g) cups semisweet chocolate chips, 2 (28g) tablespoons unsalted butter
• Remove from the heat and stir in the vanilla and salt.
  1 teaspoon vanilla extract, ½ teaspoon fine sea salt
• Allow the fudge filling to cool for 3–5 minutes until slightly thickened.

Step 4: Assemble and Bake

• Press about two-thirds of the cookie dough evenly into the prepared pan using lightly damp hands or an offset spatula.
• Spread the fudge filling evenly over the cookie layer, making sure you meet the edges.
• Pinch off pieces of the remaining cookie dough, flatten them well in your palms, and scatter them over the top. Leave small gaps so some of the chocolate filling remains visible for that classic oatmeal fudge bar look.
• If your gaps are too big you can use your fingers to flatten the cookie dough pieces gently to spread them dough.
• Bake for roughly 28-30 minutes, or until the edges are golden brown, the cookie topping is lightly browned, and the center is just set with a slight jiggle. Do not overbake or the bars will get dry.
• Sprinkle the warm bars with flaky sea salt if desired fresh from the oven.
  flaky sea salt
• Cool completely in the pan, then transfer to the refrigerator for at least an hour for the cleanest slices.
• You can spray your knife with a little cooking spray to get more clean cuts, I cut this bar in 3 rows vertically and horizontally for 9 even bars.
• Enjoy!
• Yields 9-12 bars

Notes

How to Store:

Room temperature- Keep in an airtight container for 6-7 days. Place a slice of bread in the container to keep them soft.

Freezing- store baked cooled bars in a Ziplock with all of the air removed first. Freeze for up to one month. Allow to thaw to room temperature an enjoy!

Nutrition

Serving: 1barCalories: 432kcalCarbohydrates: 56gProtein: 6gFat: 21g

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