01 - Preheat the oven to 350°F. Grease a 24-cup mini muffin pan or line it with mini paper liners.
02 - In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt until evenly mixed.
03 - In a large bowl, whisk the melted butter and sugar until fully combined. Add the eggs and vanilla extract, whisking until the mixture is smooth and glossy.
04 - Gently fold the dry ingredients into the wet mixture, stirring just until combined to avoid overmixing.
05 - Fold in the mini chocolate chips and chopped nuts if using, distributing them evenly throughout the batter.
06 - Spoon the batter evenly into the prepared mini muffin cups, filling each about three-quarters full.
07 - Bake for 13 to 15 minutes, or until the tops are set and a toothpick inserted in the center comes out with a few moist crumbs.
08 - Allow the bites to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.