Preheat oven to 425°F. Line a 12-cup muffin pan with paper liners. Add the old-fashioned oats to a food processor and process until they resemble a fine flour. Transfer the oat flour to a large mixing bowl.

Add the cottage cheese, eggs, avocado oil, maple syrup, brown sugar, and vanilla to the now-empty food processor. Process until smooth and creamy.

Add the all-purpose flour, cocoa powder, baking powder, baking soda, and salt to the bowl with the oat flour and whisk until well combined. Pour the blended wet ingredients into the dry ingredients and stir just until combined. Do not overmix.

Divide the batter evenly among the prepared muffin cups, filling each about 90–95% full.

Sprinkle the tops with the mini chocolate chips and coarse sparkling sugar, if using.

Bake at 425°F for 5 minutes. Without opening the oven door, reduce the oven temperature to 350°F and continue baking for 15–17 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.

Cool in the pan for 5 minutes, then transfer the muffins to a wire rack to cool completely.