Preheat your oven to 350°F (175°C).

In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt.

In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.

Add the egg, vanilla extract, and peppermint extract to the butter mixture, mixing until well combined.

Gradually add the dry ingredients to the wet mixture, mixing just until combined.

Fold in the chocolate chips or peppermint kisses gently with a spatula or wooden spoon.

Scoop tablespoon-sized portions of dough onto a lined baking sheet, spacing them about 2 inches apart.

Bake in the preheated oven for 10-12 minutes, or until the edges are set but the centers are still soft.

Remove from the oven and press a chocolate kiss into the center of each cookie immediately.

Allow the cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack.