Preheat Oven & Prep Pan: Preheat your oven to 350°F (175°C) and line a mini muffin pan with paper liners.
Mix Dry Ingredients: In a medium bowl, whisk together flour, cocoa powder, baking powder, baking soda, and salt.
Cream Butter & Sugar: In a large bowl, cream together butter, granulated sugar, and brown sugar until light and fluffy.
Add Eggs & Vanilla: Beat in the eggs one at a time, then stir in the vanilla extract.
Combine Wet & Dry: Gradually add the dry ingredients to the wet mixture, alternating with milk, until just combined.
Fold in Chocolate Chips: Stir in chocolate chips, if using.
Scoop Batter: Spoon batter into the prepared mini muffin pan, filling each liner about ¾ full.
Bake & Cool: Bake for 12–15 minutes or until a toothpick inserted in the center comes out clean. Cool for 5 minutes before transferring to a wire rack.
