Use a large serrated knife to remove the tops of the cake layers so that they’re flat. See my tips on how to level a cake and how to stack a cake.
Place the first cake layer on a serving plate or cardboard cake circle and top with about 1 cup of frosting. Smooth frosting into an even layer.
Add about half of the chopped Reese’s on top of the frosting and press into the frosting. Spread a small amount of frosting on top of the Reese’s so that it’s sticky on top for the next cake layer.
Add the next cake layer and top with about 1 cup of frosting. Smooth frosting into an even layer.
Add remaining half of the chopped Reese’s on top of the frosting and press into the frosting. Spread a small amount of frosting on top of the Reese’s so that it’s sticky on top for the next cake layer.
Add the final cake layer to the top of the cake.
Smooth out the frosting on the sides of the cake, creating a thin crumb coat.
Add about 1 cup of frosting to the top of the cake and smooth into an even layer.
Frost the cake using my tutorial for a smooth cake. Stop just before using the paper towel, which won’t be necessary with the pattern on the sides of this cake.
Use an offset spatula to create the stripes around the cake. For guidance, see the video above starting at about 1:40.
Set the cake aside and make the chocolate ganache (see my tips for making chocolate ganache).