Preheat the oven to 350°F and line a 12-cup muffin tin with liners.

Melt the butter and chocolate in the microwave on 50% power in 30-second intervals, stirring after each, until smooth. Let cool slightly.

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

In a large bowl, whisk eggs, sugar, brown sugar, vanilla, and peppermint extract until smooth and combined.

Stir in the cooled butter-chocolate mixture. Gradually add the dry ingredients, mixing just until combined. Stir in the buttermilk.

Divide the batter evenly among the liners and bake for 15–19 minutes, or until a toothpick inserted in the center comes out clean. Let cool completely on a wire rack.

Combine the chocolate chips and heavy cream in a small microwave-safe bowl. Heat on 50% power in 20-second intervals, stirring until smooth.

Refrigerate for 10 minutes to thicken slightly.

In a stand mixer, beat the cream cheese and butter together until fluffy. Mix in the vanilla, peppermint extract, and powdered sugar, beating for 3–4 minutes until light and fluffy.

Divide the frosting in half. Add red food coloring to one half and mix until fully combined.

Spoon a thin layer of ganache on top of each cooled cupcake.

Prepare two piping bags with the red and white frostings. Lay a sheet of plastic wrap on the counter. Pipe stripes of each frosting side by side on the plastic wrap, alternating colors. Roll the plastic wrap into a tube shape, twist one end to seal, and snip the other end where the frosting starts.

Place the frosting tube into a third piping bag fitted with your piping tip. Pipe swirls onto the cupcakes, leaving some ganache visible.

Garnish with peppermint candies.