Prepare chocolate cake as instructed. Allow to cool completely. As cake is cooling, prepare peppermint buttercream frosting.
Peppermint Buttercream Frosting
Place softened butter into the bowl of a stand mixer that has been fitted with the paddle attachment. Turn the mixer on a medium setting and cream the butter until it is smooth and has lightened in color, about 3 minutes.
Add confectioner’s sugar, ½ a cup at a time. After each cup has been incorporated, turn the mixer onto the highest speed setting and for about 10 seconds to lighten the frosting.
Add peppermint extract and a pinch of salt and combine until well-incorporated.
Add milk, heavy cream or half-and-half until the frosting has reached the preferred consistency. For a firmer frosting, add more confectioner’s sugar, a ¼ cup at a time. For a softer frosting, add more milk or cream, a tablespoon at a time.
Frost cake and sprinkle chopped peppermint bark on top of cake as garnishment (optional).
For 3 layers - I simply split the cake batter between 3 cake pans instead of 2. For 3 layers, check cake for doneness after about 25 minutes.