Melt chocolate in a heatproof bowl set over a pan of simmering water, stirring.
Whisk together flour, baking powder, and cocoa in a small bowl.
Whisk together granulated sugar, eggs, and melted butter in a medium bowl. Gradually whisk in melted chocolate and mint extract until smooth. Stir in flour mixture. Refrigerate until firm, at least 3 hours.
Preheat oven to 325 degrees. Roll tablespoons of dough into balls using your palms, then roll in confectioners' sugar to coat. Transfer to parchment-lined baking sheets, spacing each 1 inch apart. Bake until slightly firm in the center, about 15 minutes.
Let cool slightly on sheets set on wire racks. Transfer cookies to racks, and let cool completely.
Dough can be refrigerated for up to 3 days or rolled into balls and frozen for up to 2 weeks. Roll in confectioners' sugar just before baking. Cookies can be stored at room temperature for up to 3 days.
Sorry, but these cookies are boring. The chocolate flavor was rich but felt they were bland, perhaps not enough sugar in the recipe. Not worth the effort.
These cookies are delicious!!! The hint of mint is perfect with the chocolate and powdered sugar.
Also, the recipe doubled beautifully.