Preheat oven to 375℉/190℃. Butter 12 muffin cups or line them with liner papers.
Divide the mixture evenly between the muffin cups. Make the topping by tossing together sugar, pecans, and chocolate chips in a small bowl, then sprinkle evenly on top of the batter.
Bake for 15-20 minutes, or until a toothpick inserted into the center of the muffins comes out clean. Transfer pan to a wire rack and let cool for 10 minutes, then remove muffins from pan and let cool completely.
*For a dark black chocolate muffin, substitute 2 tablespoons of black cocoa powder for unsweetened cocoa powder.
Muffins will keep for 2 days in an airtight container at room temperature. They can also be frozen for up to 2 months. To thaw, leave them on the counter, still covered, or overnight in the fridge.