1. Preheat your oven to 375 F (190 C). Lightly grease a mini muffin tin (or a regular muffin tin if you want larger “donut muffins”) with butter or non-stick spray.

2. In a large mixing bowl, whisk together the all-purpose flour, 1/4 cup granulated sugar, baking powder, baking soda, and salt. Make sure there are no lumps and everything is well combined.

3. In a separate medium bowl, combine the sourdough discard, milk, 1/4 cup melted butter, and vanilla extract. Whisk until smooth and fully incorporated.

4. Pour the wet ingredient mixture into the dry ingredient mixture. Stir gently with a spoon or spatula until just combined. Be careful not to overmix; a few small lumps are perfectly fine and help keep the donut holes tender.

5. Spoon the batter into the prepared mini muffin tin cavities, filling each about two-thirds full. If using a regular muffin tin, fill each cavity about halfway. The batter will be thick, so use two spoons or a small cookie scoop for easy portioning.

6. Place the muffin tin in the preheated oven and bake for 12-15 minutes for mini donut holes, or 15-20 minutes for regular-sized ones. They are done when a toothpick inserted into the center comes out clean and the tops are lightly golden brown and spring back when gently pressed.

7. While the donut holes are baking, prepare the cinnamon sugar coating. In a shallow bowl, combine the 1/2 cup granulated sugar and 1 teaspoon ground cinnamon. In another shallow bowl, melt 1/4 cup of butter for dipping.

8. Once baked, remove the donut holes from the oven and let them cool in the tin for just 2-3 minutes. While still warm, gently remove them from the muffin tin. Dip each donut hole first in the melted butter, allowing any excess to drip off, then roll it generously in the cinnamon sugar mixture until fully coated. Serve immediately and enjoy!