In your stand mixing bowl or a large mixing bowl, add the milk, sourdough discard, egg yolk, unsalted butter, and sugar. Give everything a whisk, it's okay if its lumpy the goal here is to just break up the butter into bits and whisk in the egg and discard.
¼ (57g) cup salted butter, 1 egg yolk, ½ (120g) cup sourdough discard (100% hydration), ¼ (60g) cup sour cream, ¾ (180g) cup whole milk, 1 (12g) tbsp granulated sugar
After you combine the wet ingredients, add the flour, baking powder, baking soda, salt, garlic powder, onion powder, and Italian seasoning to the bowl. You'll want to mix this dough by hand or with a stand mixer on low with a dough hook until a rough dough forms, this takes about 2-3 minutes. Scrape down the sides of the bowl to make sure all of the ingredients are getting incorporated, and mix another 5-6 minutes by hand or with the stand mixer on low. Your dough should be smooth, tacky, and the butter worked in by the time you're done mixing.
3¼ (400g) cups all-purpose flour, ¾ tsp baking powder, ½ tsp baking soda, 3/4 tsp fine sea salt, 1 tsp garlic powder, ½ tsp onion powder, 1 tsp Italian seasoning
Once your dough has come together, it's important to cover the bowl with plastic and let it rest for 30 minutes in the refrigerator to let the gluten rest and bond. This is key to achieving a dough that you can shape, so don't skip this step!
Optional Overnight Fermentation: If you would like to let this dough cold ferment longer, simply prepare the dough a day ahead and cover and refrigerate overnight. When you're ready to shape your wreath, remove dough from the fridge and continue with the steps listed below.