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

2. In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt until evenly distributed.

3. In a separate medium bowl, whisk together the cottage cheese, milk, melted butter, large egg, and vanilla extract until well combined.

4. Pour the wet ingredient mixture into the dry ingredient mixture. Stir gently with a spatula or wooden spoon until just combined. Do not overmix; a few lumps are fine.

5. Gently fold in your chosen mix-ins, such as berries, chocolate chips, or nuts, distributing them evenly throughout the batter. Avoid overmixing.

6. Divide the batter evenly among the 12 prepared muffin cups, filling each about two-thirds full.

7. Bake for 20-25 minutes, or until a wooden skewer or toothpick inserted into the center of a muffin comes out clean. The tops should be golden brown and spring back lightly when touched.

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.