Prepare and bake the cupcakes according to the directions on the box. Allow them to cool completely before decorating.

In a large mixing bowl, beat the butter on medium speed for about 1 minute using a stand mixer or hand mixer. Add half of the confectioners’ sugar and mix until fully combined, then add the remaining sugar and beat until smooth.

Mix in the vanilla extract and 1 tablespoon of milk. Continue adding milk, 1 tablespoon at a time, until the frosting reaches your desired consistency.

Divide the frosting. Place half into one piping bag. Divide the remaining frosting between two bowls, tinting one with red food coloring and the other with green. Mix until the colors are fully incorporated, then transfer each color to its own piping bag.

Cut 12 medium squares of parchment paper. Pipe a single layer of plain frosting onto the center of each cupcake. Gently press each cupcake upside down onto a piece of parchment paper to slightly flatten the top. Place the cupcakes in the freezer for 10–15 minutes, until firm.

Remove the cupcakes from the freezer and carefully peel away the parchment paper.

Decorate as desired. Roll some cupcakes gently in gold sanding sugar for a sparkling effect. Use the red and green frosting to pipe festive designs, and decorate with M&Ms in patterns or mixed colors. Press a mini Reese’s Peanut Butter Cup into the top of each cupcake to create the ornament “hanger.”

Serve and enjoy!