1. 1. Prepare Your Muffin Tin: Preheat your oven to 375 F (190 C). Line a 12-cup standard muffin tin with paper liners or grease it thoroughly with butter or non-stick spray. This prevents sticking and makes cleanup easier.

2. 2. Combine Dry Ingredients: In a large mixing bowl, whisk together the 1 1/2 cups all-purpose flour, granulated sugar, baking powder, baking soda, and salt. Make sure there are no lumps and the ingredients are evenly distributed.

3. 3. Mix Wet Ingredients: In a separate medium bowl, whisk together the egg, milk, sourdough discard, melted and cooled butter, and vanilla extract until well combined and smooth. The discard might have some small lumps, which is perfectly fine.

4. 4. Combine Wet and Dry: Pour the wet ingredients into the dry ingredients. Stir gently with a spatula or wooden spoon until *just* combined. The batter will be thick and lumpy, and that’s exactly what you want. Overmixing will lead to tough muffins, so stop as soon as you no longer see streaks of dry flour.

5. 5. Add the Blueberries: In a small bowl, toss the blueberries with the extra tablespoon of flour. This step helps prevent the blueberries from sinking to the bottom of the muffins during baking. Gently fold the floured blueberries into the batter until evenly distributed.

6. 6. Fill Muffin Cups: Divide the batter evenly among the 12 prepared muffin cups. You can use an ice cream scoop for easy portioning, filling each cup about two-thirds full.

7. 7. Bake Until Golden: Bake for 20-25 minutes, or until the tops are golden brown and a wooden skewer or toothpick inserted into the center of a muffin comes out clean.

8. 8. Cool and Serve: Allow the muffins to cool in the muffin tin for 5 minutes before transferring them to a wire rack to cool completely. Enjoy them warm or at room temperature.