First, prepare three 8-inch cake pans by lining them with parchment paper and greasing the sides. Preheat your oven to 350°F (176°C).

Cream together the butter and sugar in a large mixing bowl for about 3-4 minutes until light and fluffy.

Mix in the sour cream, vanilla extract, and peppermint extract until well combined.

Add the egg whites in two batches, ensuring each is blended well before adding the next.

In a separate bowl, combine the dry ingredients.

In a measuring cup, mix the milk and water together.

Fold half of the dry ingredients into the batter, then add the milk mixture and mix until combined. Finally, fold in the remaining dry mix.

Divide the batter evenly among the cake pans, and bake for 21-23 minutes or until a toothpick comes out clean.

Let the cakes cool in the pans for 2-3 minutes before transferring to wire racks to cool completely.

Beat the salted butter and shortening together until creamy.

Sift in half of the powdered sugar, mixing until smooth.

Add 3-4 tablespoons of water, vanilla extract, and peppermint extract, mixing until smooth.

Gradually add the remaining powdered sugar, mixing and adding more water as needed to achieve a silky consistency. Stir in the peppermint pieces.

Trim the domes off the top of each cake layer until flat.

Place the first layer on a serving plate and spread about 1 cup of frosting on top.

Add the second layer, topping it with another cup of frosting, then place the final layer on top and frost the entire cake with the remaining frosting.

Melt the white chocolate chips with the heavy cream, whisking to form a ganache. Add red gel icing color to reach desired shade.

Let the ganache thicken and drizzle it around the edges of the cake.

Use leftover frosting to pipe a ring around the cake, then arrange candies on top.