How to Make It
Preheat oven to 350°F. Grease two 8-inch round metal cake pans with cooking spray and line the bottoms of each pan with 8-inch circles of parchment paper. Set aside.
Prepare cake mix according to package instructions with water, oil, and eggs. Pour batter into prepared cake pans. Bake until a toothpick inserted comes out clean, 26 to 31 minutes. Allow cake layers to cool completely, about 45 minutes.
While layers are cooling, place Oreo cookies in a food processor and process until fine crumbs. (Note: you can also crush the cookies in a large sealable bag.) Set aside.
Once layers have cooled, place one cake layer on a cake stand. Spread 1/2 cup frosting across the cake layer. Add second layer and use remaining frosting to cover entire cake. Coat the sides of the frosted cake in Oreo cookie crumbs by gently pressing handfuls of the crumbs against the frosting on the sides of the cake, moving around the perimeter and recollecting crumbs that don’t stick.
Use some of the remaining crumbs to line the bottom edge of the cake that touches the cake stand to give the illusion of loose soil. Place 3 mounds of crumbs on top of the cake. Use black decorating icing to write gravestone messages on the faces of the Milano cookies, and stick the cookies into the mounds of crumbs so the bottoms of the cookies go into the cake and stand upright.