Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.

In a medium bowl, whisk together the gluten-free flour, cocoa powder, baking powder, and salt.

In a stand mixer or with a hand mixer, cream the softened butter and sugar until light and fluffy (about 2–3 minutes).

Beat in the egg, vanilla, and peppermint extract until combined.

Gradually add the dry ingredients and mix just until a smooth dough forms. If it feels sticky, chill for 15–20 minutes.

Roll dough into small balls (about 1 tablespoon each) and flatten slightly to form thin discs.

Place cookies 1 inch apart on prepared sheets. Bake for 9–11 minutes; cookies will firm as they cool.

Let cookies cool on the sheet for 5 minutes, then transfer to a wire rack.

Melt chocolate and coconut oil together in short bursts in the microwave, stirring between each, or use a double boiler.

Using a fork or dipping tool, coat each cooled cookie in chocolate, tapping off excess. Return to rack until set. For an ultra-smooth finish, refrigerate briefly.