1. Preheat your oven to 375 F (190 C). Line a 12-cup muffin tin with paper liners or grease it thoroughly with butter or non-stick spray.

2. In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt. Make sure there are no lumps and everything is evenly distributed.

3. In a separate medium bowl, whisk together the egg, milk, sourdough discard, melted and cooled butter, and vanilla extract until well combined. The mixture should be smooth and uniform.

4. Pour the wet ingredients into the dry ingredients. Stir gently with a spatula or wooden spoon until just combined. It’s okay if there are a few lumps; overmixing develops gluten, which can make muffins tough. Stop stirring as soon as you no longer see streaks of dry flour.

5. Gently fold in the diced fresh strawberries. Distribute them evenly throughout the batter without mashing them.

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

7. Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until the tops are golden brown and a wooden skewer inserted into the center of a muffin comes out clean.

8. Once baked, remove the muffin tin from the oven and let the muffins cool in the tin for 5 minutes before transferring them to a wire rack to cool completely. Enjoy them warm or at room temperature.