These festive cookies are the perfect addition to any holiday cookie exchange.
Melt 2/3 cup (150 mL) mint chips and butter in heatproof bowl set over simmering water. Cool to room temperature.
Whisk together flour, cocoa powder, baking powder and salt until blended; set aside. Beat together eggs, brown sugar, granulated sugar and vanilla in large bowl using electric mixer until well incorporated. Beat in melted chocolate mixture. Beat in flour mixture just until combined.
Refrigerate dough for 2 to 3 hours or until well chilled and firm.
Vary the size of the cookies to make bite-size minis using halved mini marshmallows.
Preheat oven to 350°F (180°C). Roll 2 tablespoonfuls of dough at a time into balls; transfer to parchment paper–lined baking sheet, about 2 inches (5 cm) apart. Press lightly to flatten.
Bake in batches for 8 to 10 minutes or until cookies are set at edges. Press marshmallow half on top of each cookie. Bake for 1 to 2 minutes or until cookie tops are set and marshmallows are soft.
After marshmallows are pressed onto cookies, broil for 1 to 2 minutes until marshmallows are golden. Top with melted chocolate.
Cool cookies in pan for 5 minutes. Transfer to rack; cool completely.
Melt remaining mint chips in heatproof bowl set over simmering water. Drizzle chocolate generously over cookies. Garnish with holiday shapes. Serve when chocolate is set.