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Sourdough S’mores Brownies

These Sourdough S’mores Brownies have all the nostalgia of sitting around a campfire, but in one easy dessert. They start with a buttery graham cracker crust, then topped with a rich, fudgy sourdough brownie layer, and are topped with marshmallows that get toasted to ooey gooey perfection.
5 from 1 vote
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Prep Time 25 minutes
Cook Time 40 minutes
Servings 12

Equipment

  • 9×9-inch baking pan - to bake your brownies. I love this pan 9x9 pan from USA Bakeware.
  • Food processor or rolling pin - to crush the graham crackers for the crust.
  • Parchment paper - to line your brownie pan for easy removal.
  • Mixing bowls - to mix the brownie batter and graham cracker crust.
  • Whisk - to mix the batter.
  • Spatula - to spread the brownie batter.
  • 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.
  • Kitchen torch (optional) - for browning the marshmallows. I like this kitchen butane torch, but you can also use your oven broiler.

Ingredients
  

Sourdough Graham Cracker Crust:

  • 10 (150g) crackers sourdough graham crackers finely crushed
  • 6 (85g) tablespoons unsalted butter melted
  • 2 (25g) tablespoons granulated white sugar
  • 1/8 tsp fine sea salt

Sourdough Brownie:

  • ½ (113g) cup unsalted butter
  • ½ (120g) cup semi-sweet chocolate chips
  • ½ (42g) cup unsweetened cocoa powder
  • 1½ (300g) cups granulated white sugar
  • ¼ (50g) cup light brown sugar
  • ½ (120g) cup sourdough discard (100% hydration)
  • 3 large eggs
  • 2 teaspoons cornstarch
  • 1 teaspoon vanilla extract
  • 1 (125g) cup all-purpose flour
  • 1½ teaspoons fine sea salt

Sourdough Discard Swap:

  • 1/4 (60g) cup whole milk
  • 1/4 (30g) cup all-purpose flour

Marshmallow Topping:

  • 1 10 oz (283g) bag large marshmallows or minis see notes

Garnish:

  • ¾ (125g) cup milk chocolate or semi-sweet chocolate pieces
  • 2 graham crackers crushed

Instructions
 

Step 1: Make the Graham Cracker Crust

  • Note: To make this recipe, you'll need one batch of Sourdough Graham Crackers. Head over to the recipe and mix a batch before proceeding with the bars or you can substitute your favorite store bought brand.
  • Preheat the oven to 350°F (175°C). Line a 9x9-inch baking pan with parchment paper (this is key to a clean release of the bars).
  • In a food processor, add the prepared sourdough graham crackers or your choice of grahams. Pulse until the graham crackers are very fine. You can also do this by adding the graham crackers to a plastic Ziplock and crushing them with a rolling pin until fine.
    10 (150g) crackers sourdough graham crackers
  • Add the melted butter, sugar, and salt to the graham cracker crumbs. Pulse in the food processor until the mixture starts to clump together. You can also do this by adding all of the ingredients to a bowl and mixing with a spatula to bring the crust together.
    6 (85g) tablespoons unsalted butter, 2 (25g) tablespoons granulated white sugar, 1/8 tsp fine sea salt
  • Press the graham cracker crust firmly into the bottom of the prepared pan. You can use the bottom of a cup or a measuring cup to help press the crust and get it nice and packed down.
  • Bake the crust for 10 minutes, then set aside to cool while you prepare the brownie batter.

Step 2: Mix and Bake the Brownie

  • In a medium saucepan or microwave-safe bowl, melt the butter until just melted.
    ½ (113g) cup unsalted butter
  • Add the semi-sweet chocolate chips and cocoa powder to the melted butter. Whisk over low heat, or microwave in short bursts, until the chocolate has just melted and the mixture is smooth.
    ½ (120g) cup semi-sweet chocolate chips, ½ (42g) cup unsweetened cocoa powder
  • Transfer from heat as soon as the chocolate has melted if you used a pot, then pour the mixture into a mixing bowl.
  • Whisk in the granulated sugar, brown sugar, sourdough discard, eggs, and vanilla extract until the brownie batter is shiny and smooth.
    1½ (300g) cups granulated white sugar, ¼ (50g) cup light brown sugar, ½ (120g) cup sourdough discard, 3 large eggs, 1 teaspoon vanilla extract
  • Add the flour, cornstarch, and salt to the brownie batter, and mix just until no streaks remain. Try not to overmix at this point or the brownies will be tough. You just want the flour incorporated.
    2 teaspoons cornstarch, 1 (125g) cup all-purpose flour, 1½ teaspoons fine sea salt
  • Sourdough Discard Swap Option: If you don't have sourdough discard, add the extra flour and milk at this time and mix it into the brownie batter.
  • Spread the brownie batter over the graham cracker crust, making sure it reaches the edges. Smooth the top with a spatula.
  • Overnight Fermentation Option: If you want to ferment this brownie batter, cover with plastic and refrigerate overnight in the pan. When you're ready to bake your brownie, allow to rest at room temperature for about an hour to warm up then bake as instructed.
  • Transfer the brownies to the hot oven, and bake at 350°F for 35-40 minutes, or until the edges are set, the center no longer jiggles, and a toothpick inserted in the center comes out with moist fudgy crumbs.
  • Do not bake until the toothpick comes out completely clean. These brownies are meant to be fudgy and will continue to set as they cool. Baking time my vary on your oven, my brownies are done anywhere between 35-40 minutes.
  • Cool the brownies for at least 20 minutes or up to 24 hours before adding the marshmallows.

Step 3: Top with Marshmallows

  • Make sure your oven is still preheated to 350°F (175°C).
  • Line the entire top of the brownie with even rows of marshmallows, until no gaps remain.
    1 10 oz (283g) bag large marshmallows
  • Note: If you want a thinner layer of marshmallows, you can either cut them in half and layer them on top or use minis.
  • Transfer the pan to the oven for 5-8 minutes, until the marshmallows are melty and start to puff.
  • If you want to use your oven to toast the marshmallows, turn your oven to broil at about 450 F.
  • Watching very closely, toast the tops of the marshmallows until golden about 1-3 minutes. Immediately remove from the oven once the tops are golden. A word of caution if you're using your oven broiler, it's very easy to burn the marshmallows so watch the entire time!
  • Alternatively you can use a butane kitchen torch and torch the tops of the marshmallows until golden.
  • Sprinkle the top of the warm marshmallows with the chopped milk chocolate (or semi-sweet chips) and crushed graham crackers.
    ¾ (125g) cup milk chocolate or semi-sweet chocolate, 2 graham crackers
  • Allow the brownies to cool at least 30 minutes to an hour so the marshmallows can set up before slicing and serving.
  • Yields 12 brownies

Notes

How to Store:
Room Temperature- Store in an airtight container up to 3 days. Be careful about these brownies sitting in a warm environment, the topping can melt.
Refrigerator- Keeps up to 5 days in an airtight container in the refrigerator. To enjoy warm, microwave individual brownies for 10–15 seconds to soften the marshmallow and chocolate.
Freezer- You can freeze the unfrosted brownies by wrapping them tightly and freezing for up to 2 months. Thaw in the refrigerator overnight, then add marshmallows as directed. Enjoy!

Nutrition

Serving: 1brownieCalories: 570kcalCarbohydrates: 89gProtein: 6gFat: 23g
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