White chocolate peppermint cake layers with a white chocolate peppermint pretzel filling and a white chocolate peppermint buttercream.
Pre-heat oven to 350 degrees. Spray four 6-inch round cake pans or three 8-inch round cake pans with nonstick spray, line the bottom of the pans with parchment paper and spray again. Set aside
Whisk together the dry ingredients and set aside.
Turn the mixer to medium-low, add in the whole eggs, egg yolks, vanilla, peppermint extract and the melted white chocolate. Stop the mixer and scrape down the sides of the bowl.
With the mixer on low, alternate add in the dry ingredients and buttermilk in 3 batches, ending and starting with the dry ingredients. Mix until just combined.
Pour batter into prepared pans (about 16 ounces in each 8-inch pan or 12 ounces in each 6-inch pan) and bake until slightly golden in on top, 20 to 22 minutes. (A few moist crumbs should come out on a toothpick when testing the centers).
In a microwave safe bowl, heat the cream and the pour it over the white chocolate to melt. Stir until the mixture is smooth and silky. If needed heat the mixture for another 20 to 30 seconds and stir until the chips are melted. Set aside.
Add the white chocolate ganache, followed by the peppermint extract and then increase the speed to medium-high and beat the frosting for about 3 to 5 minutes, until light in color and texture.
Heat the oven to 250 degrees F. Line a baking sheet with parchment paper. Set aside.
In a medium sized bowl, combine 1 cup milk powder, pretzel crumbs, corn starch, sugar and salt. Toss with your hands to mix. Add the melted butter and toss, using a spatula or spoon, until the mixture starts to come together and form small clusters.
Spread the clusters on a parchment lined sheet pan and bake for 20 minutes. The crumbs should be sandy at that point. Cool the crumbs completely.
Crumble any clusters that are larger than 1/2 inch in diameter, and put the crumbs back in the medium bowl. Add the 1/4 cup milk powder and toss together until it is evenly distributed throughout the mixture.
Pour the white chocolate over the crumbs and toss until your clusters are covered. Add the crushed peppermint. Then continue tossing them every five minutes until the white chocolate hardens and the clusters are no longer sticky. The crumbs will keep in an airtight container in the fridge or freezer for up to 1 month.
Place the first cake layer, top side up, on a cake board and evenly spread about 3/4 cup of the buttercream over the cake. Sprinkle about 1/2 cup of the pretzel filling over the frosting and press down lightly with your fingers to create a level surface.
Repeat these steps with the second cake layer. Place the final cake layer top-side down.
Finish frosting the cake with the remaining buttercream and top with remaining pretzel filling.