Peppermint cake - Preheat the oven to 350 degrees. Melt the 6 oz of white chocolate with ¼ c of the milk in the microwave in a safe bowl in 20 second increments until it is smooth. Set aside to cool. In another bowl, mix together the flour, baking powder and salt. Set to the side.
Cream butter and sugar together until they are light and fluffy, about 2-3 minutes. Add in the eggs, one at a time and thoroughly combine, scraping down the sides of the bowl as you go. Add in the vanilla and cooled white chocolate and mix.
Using a spatula to fold in the ingredients, starting and ending with the dry ingredients, alternate between the flour mixture first, then the milk until all ingredients are incorporated together.
Evenly divide the batter between 2- 9” cake pans (either lined with parchment paper - or nonstick). Bake in a 350 degree oven for 22-25 minutes, or until a toothpick comes out clean. Run a knife around the edge and release to be placed on a cooling rack until at room temperature.
Peppermint Mousse - In a small pan over low heat, melt the white chocolate, sour cream, and half of the whipping cream together. Continually stir until it is just melted, then remove from heat. Allow to cool and stir on occasion for about 20 minutes until it has come to room temperature.
In a medium bowl, whip the remaining cream until it is light and fluffy. Add the finely crushed peppermint candies. Gently fold in the cooled white chocolate mixture and place in the refrigerator for about 2 hours to chill until almost set.
Assemble - Take the first layer and place in the center of the cake plate flat side up. Cover the top with the peppermint mousse. Place the top layer of cake, flat side down evenly on top.
Frosting - Using an offset spatula coat the top and side with an even layer of frosting. (use link above for homemade or use a ready made tub of vanilla and sprinkle crushed candy canes on top)
Using your hands, scoop up a small handful of peppermint candies and gently press into the side of the cake, firmly enough for them to stick to the frosting. Repeat until the entire side of the cake is coated in candies.
Place in the refrigerator for about an hour to allow frosting to set before serving. Store in the refrigerator until ready to eat.