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

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

In another bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy.

Add the egg, vanilla, and milk to the butter-sugar mixture; mix until combined.

Slowly add the dry ingredients to the wet ingredients, stirring gently until a soft dough forms. Optional: fold in mini chocolate chips.

Cover the bowl with plastic wrap and refrigerate the dough for about 30 minutes.

Roll the chilled dough into 1-inch balls and place them on the prepared baking sheets, spacing 2 inches apart.

Bake for 8-10 minutes until edges are set and centers are slightly soft.

Press a peppermint-striped chocolate kiss into the center of each cookie right after removing from the oven.

Sprinkle tops with crushed peppermint candies while still warm.

Cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.