Prepare the cake mix following the package instructions. Combine the mix, eggs, oil, and water (or other ingredients listed on the box) in a mixing bowl and stir until smooth. Gently fold in the semisweet chocolate chips.

Divide the batter evenly among the cupcake liners, filling each about ⅔ full. Bake in the preheated oven for 14 - 19 minutes, or until a toothpick inserted in the center comes out clean. Remove the cupcakes from the oven and let them cool completely.

Line three baking sheets with parchment paper. In a microwave-safe bowl, melt the black candy melts in 30-second intervals, stirring between each interval until smooth. Transfer the melted candy into a piping bag fitted with a Wilton #4 tip.

On the first prepared baking sheet, pipe antler shapes about 1 ½ inches long. Let the antlers set.

In a double boiler, melt the dark chocolate wafers until smooth. Dip each Nutter Butter into the melted chocolate, coating it completely. Place the dipped cookies onto the second prepared baking sheet.

Decorate each cookie by adding two black sugar pearls for eyes near the top of the cookie and an M&M for the nose (red or brown). Carefully peel the antlers from the parchment paper and attach them near the top of the cookie above the eyes. Place the decorated cookies in the refrigerator for 10 minutes to allow the chocolate to set.

To make the frosting, beat the room-temperature butter in a large mixing bowl with a hand mixer or stand mixer until smooth. Gradually add the powdered sugar, mixing on low speed until combined. Add the cocoa powder and mix again. Incorporate the peanut butter, vanilla extract, and one tablespoon of heavy cream, then beat the mixture on high speed until fluffy. Add another tablespoon of heavy cream if needed for the desired consistency.

Once the cupcakes have cooled, frost them using a spatula or a piping bag. Add holiday sprinkles to the frosting, then top each cupcake with a Nutter Butter reindeer.