Preheat the oven to 350 degrees Fahrenheit. Line two cupcake tins with black cupcake liners.

In a large mixing bowl, combine the 15.25-ounce chocolate cake mix, 3 large eggs, 1 cup chocolate milk, and 1/3 cup vegetable oil. Mix about 2 minutes until completely combined.

Scrape the sides and bottom of the bowl occasionally with a spatula while mixing.

Scoop the batter into the prepared liners, filling each about 2/3 full. Do not overfill.

Bake 18–25 minutes, or until a toothpick inserted into the center of a cupcake comes out clean.

Remove cupcakes from the oven and let them cool in the pans briefly, then transfer to a wire rack and allow to cool completely before decorating.

While the cupcakes cool, cut each of the 12 large marshmallows in half crosswise to make 24 marshmallow halves.

Fit a piping bag with a Wilton 2A tip and fill it with the whipped white frosting from the two 14-ounce tubs.

Place one marshmallow half, cut side down, in the center of the top of each cooled cupcake.

Pipe frosting around the base of the marshmallow, then pipe in a gradual inward spiral over the marshmallow to form a ghost-like, ice-cream-style swirl.

Press two brown Mini M&Ms into the front of the frosting spiral on each cupcake to make the eyes (use 48 brown Mini M&Ms total).

Repeat steps 9–11 until all cupcakes are decorated.