1. In a large mixing bowl cream together the softened butter and sugar until fluffy (2-3 minutes).
2. Next, beat in the yolks, vanilla extract, and sourdough discard until combined.
3. To a seperate bowl whisk together flour, baking soda, cream of tartar, salt, and cornstarch.
4. Add the dry mixture to the wet and mix until a dough is formed.

5. Cover with plastic wrap and place in the refrigerator for 1 hour (you can refrigerate the dough for up to 24 hours.

   TIP: If you would like to roll the dough out and use cookie cutters you can separate the dough into 2 even balls, create a disc shape, wrap it in plastic wrap, and place it into the refrigerator. The bake time will be 10-12 minutes.

Shape & bake the soft sourdough sugar cookies

1. Once the dough is ready, preheat the oven to 350 degrees F and line a baking sheet with parchment paper.

   If the dough has been refrigerated for longer than 1 hour let it rest for 15-20 minutes to take the chill off.

2. I like to weigh each cookie to ensure they’re exactly 60 grams, but you can also use a large cookie scoop—about 2 ounces—to portion them out evenly.

   Pro tip: Gently roll each dough portion by hand to create perfectly round cookies.

3. If you’re skipping the frosting, roll each dough ball in sugar before baking for a sparkly finish.
4. Align about 6-8 cookies on your baking sheet (making sure they are spaced about 2 inches apart) and bake for 15 minutes. If making smaller cookies, adjust the time accordingly (they may only need 8-10 minutes).
5. Remove the cookies from the oven and firmly tap the tray on the counter to create those signature bakery-style cracks. This step is optional, but it adds a beautiful finish to the cookies.
6. Place the cookies back in the oven for 3-5 more minutes to ensure they are done baking. Every oven is different, so yours might only need the initial 15 minutes.
7. Upon removing them from the oven let them rest on the pan for 5 minutes before placing on a cooling rack.

How to make the buttercream frosting

1. In a medium bowl, cream the softened butter until smooth (2-3 minutes).
2. Add the powdered sugar, salt, and vanilla extract and mix on low until incorporated, then increase speed and beat until smooth.
3. Add 1 tablespoon of heavy cream and beat another 1-2 minutes until light. If it is too stiff, add more cream 1 tablespoon at a time. If it is too soft, add up to 40 grams more powdered sugar. If using food coloring add it during this step.
4. Taste and adjust salt if needed (this keeps it from being too sweet).
5. Once the sourdough sugar cookies are completely cooled, frost each cookie generously and top with festive sprinkles if desired!

Storage Instructions

1. Unfrosted cookies: Store in an airtight container at room temperature for up to 5 days. Layer with parchment paper to keep them from sticking together.
2. Frosted cookies: Store in a single layer in an airtight container in the refrigerator for up to 5 days. Let come to room temperature before serving for the best texture and flavor.
3. Freezing: Both frosted and unfrosted cookies freeze well for up to 2 months. Thaw in the fridge overnight (for frosted cookies) or at room temperature (for unfrosted).