Preheat oven to 350 degrees F. Cut parchment paper to fit the bottom of two 8-inch round baking pans. Coat with nonstick cooking spray.

In a large bowl, combine the cake mix, buttermilk, oil, and eggs. Evenly distribute between the two prepared pans and bake for approximately 34 minutes or until a toothpick inserted in the center comes out clean.

In the meantime, carefully take apart the regular and mini Oreos, making sure the filling stays intact. Place the halves without the filling in a resealable plastic bag and smash them into crumbs. Set aside.

Remove cake from oven and cool in pans on a baking rack for 15 minutes. Remove cake from pans and peel off the parchment. Cool completely.

While cake is cooling, make the frosting. With a hand mixer, beat together the butter, powdered sugar, and milk on low until just combined. Then on high for 3 more minutes until fluffy. Set aside one tablespoon of the mixture.

Trim off a top layer from each cake to make them flat. Place one layer on a cake stand. Spread 3/4 cup of the frosting evenly over the top; sprinkle with the cookie crumbs, pressing slightly into the frosting. Place second cake layer on top, then spread the remaining frosting over the top and sides of the cake.

With a bit of the reserved frosting, secure one of the M&M’s to each of the 20 Oreo halves. Arrange on the cake so they look like pairs of eyeballs.

Slice, serve, and enjoy! Refrigerate any leftovers.