01 - Preheat the oven to 350°F. Grease a 24-cup mini muffin pan or line 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 eggs and vanilla extract; whisk until smooth.
04 - Gradually fold the dry mixture into the wet ingredients until just blended. Avoid overmixing to maintain a tender texture.
05 - Stir in the semi-sweet chocolate chips and nuts if using, distributing them evenly throughout the batter.
06 - Divide the batter evenly among mini muffin cups, filling each about three-quarters full.
07 - Bake for 12 to 15 minutes, or until the tops are set and a toothpick inserted into the center comes out with moist crumbs.
08 - Allow the bites to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.