While the cake layers bake and cool, make the candy cane buttercream.
Beat 2 cups of unsalted butter on a medium speed for 30 seconds with a paddle attachment until smooth.
Mix in 2 tsp peppermint extract, 1 tsp vanilla extract, and 1 tsp salt on a low speed.
Gradually mix in 7 cups of powdered sugar and 1/4 cup of heavy cream on a low speed.
Continue to mix on a low speed for a few minutes until the desired consistency is reached.
If the frosting seems too thick, add additional cream (1 Tbsp at a time). If the frosting is too thin, add more powdered sugar (a quarter of a cup at a time).
This step is optional, but if you want your frosting to have a little texture and don't need to pipe with it, fold crushed candy canes or peppermint candies into the frosting with a rubber spatula.
Cover the buttercream flush with plastic wrap or immediately place it in a piping bag. Otherwise, it will crust if it’s left sitting out!