01 - Preheat oven to 350°F. Grease a 24-cup mini muffin tin or line with mini paper liners.
02 - Place butter and chopped chocolate in a heatproof bowl over a pot of simmering water. Stir until smooth and melted, then remove from heat and cool slightly.
03 - Whisk sugar, eggs, vanilla extract, and peppermint extract into the melted chocolate mixture until thoroughly combined.
04 - Sift flour, cocoa powder, and salt into the batter. Fold gently until just combined, being careful not to overmix.
05 - Distribute batter evenly among prepared muffin cups, filling each about 3/4 full. Bake for 12 to 15 minutes until tops are set and a toothpick inserted comes out with moist crumbs.
06 - Let brownie bites rest in the tin for 5 minutes, then transfer to a wire rack to cool completely.
07 - Place chopped chocolate in a small bowl. Heat cream in a small saucepan until steaming, then pour over chocolate. Let stand 1 minute, add peppermint extract, and stir until smooth and glossy.
08 - Spoon or pipe ganache onto each cooled brownie bite. Garnish with mint leaves or chocolate shavings if desired. Allow ganache to set before serving.