Instructions:
1. Preheat your oven to 350°F (175°C) and line a muffin tray with paper liners or lightly grease it.
2. In a medium saucepan, melt the butter over medium heat. Remove from heat and stir in both sugars until smooth.
3. Allow the sugar-butter mixture to cool slightly before adding the eggs, one at a time, stirring well after each addition.
4. Stir in the vanilla extract.
5. In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt.
6. Gradually fold the dry ingredients into the wet mixture until just combined. Be careful not to overmix.
7. Fold in the chocolate chips, if using.
8. Scoop the batter into the prepared muffin tin, filling each cup about ¾ full.
9. Bake for 20-25 minutes, or until a toothpick inserted into the center comes out with moist crumbs attached.
10. Allow the muffins to cool in the tin for about 10 minutes before transferring to a wire rack to cool completely.
