Prep your pan and oven. Heat the oven to 350°F (175°C). Grease a 24-cup mini muffin tin well with nonstick spray or butter. Lightly dust with flour if your pan tends to stick.

Cream the butter and sugars. In a large bowl, beat the softened butter, granulated sugar, and brown sugar until light and fluffy, about 2–3 minutes. This traps air and helps the cups rise.

Add egg and vanilla. Mix in the egg and vanilla until smooth, scraping the bowl as needed.

Combine dry ingredients. In a separate bowl, whisk flour, baking soda, baking powder, and salt. Add to the wet ingredients and mix on low just until combined. Don’t overmix.

Fold in chips and extras. Stir in mini chocolate chips and any festive add-ins like M&M minis or sprinkles.

Portion the dough. Use a small cookie scoop or spoon to drop about 1 tablespoon of dough into each mini muffin cup. The cups should be about 2/3 full.

Bake. Bake for 9–11 minutes, until the edges are set and lightly golden but the centers still look soft. They’ll continue to cook in the pan.

Create the “cup.” Right out of the oven, use the back of a teaspoon or a small round measuring spoon to gently press a well into each cookie, forming a cup shape. Work carefully so you don’t crack the edges.

Cool. Let the cookie cups cool in the pan for 10 minutes, then loosen edges with a small knife and transfer to a wire rack to cool completely.

Make your filling. For buttercream or peppermint cream, beat butter until creamy. Add powdered sugar, milk, and extract (vanilla or peppermint). Whip until smooth and pipeable. For ganache, heat cream until steaming, pour over chocolate chips, rest 2 minutes, then stir smooth. Cool to thicken slightly.

Fill and decorate. Spoon or pipe the filling into each cup. Add sprinkles, crushed peppermint, or mini candy canes. Let ganache set for 20–30 minutes before stacking.