Prepare Kisses: Begin by freezing your peppermint kisses for at least 2 hours. Lay them flat on a baking sheet to prevent sticking.

Mix Wet Ingredients: In a large mixing bowl, cream together the unsalted butter, granulated sugar, and light brown sugar until light and fluffy. Add egg yolks and vanilla, mixing until smooth.

Combine Dry Ingredients: In another bowl, whisk together all-purpose flour, cocoa powder, fine sea salt, baking powder, and baking soda. Gradually fold dry mixture into the wet mixture until smooth.

Chill Dough: Cover the dough and refrigerate for at least 3 hours, or overnight if possible, to prevent spreading during baking.

Form and Bake Cookies: Preheat oven to 350°F (175°C). Scoop dough into 1-inch balls and place on a parchment-lined baking sheet. Bake for 7-8 minutes until edges are set.

Add Kisses: Press a frozen peppermint kiss into each warm cookie. Let cookies rest on the baking sheet for 5 minutes to soften the kisses.

Cool Completely: Transfer cookies to wire racks and let them cool completely.