Step 1
Preheat oven to 350 degrees F (175 degrees C). Grease and line 4 8-inch round cake pans with parchment paper.
Step 2
Combine white cake mix egg whites vegetable oil milk and vanilla extract in a large mixing bowl. Beat for 30 seconds using an electric mixer on low speed. Increase mixer speed to medium and beat for 2 more minutes. The batter will still be slightly lumpy.
Step 3
To make the red cakes measure half the batter into a separate bowl and whisk in red food coloring. Evenly transfer the red batter into 2 of the 8-inch prepared cake pans; smooth tops of batter with a spatula. Transfer half of the remaining uncolored batter into a 3rd prepared cake pan; smooth top as before. This will be the white cake portion.
Step 4
Add blue food coloring to the remaining uncolored batter in the large mixing bowl; fold 1 cup white chocolate chips into blue batter until combined. Transfer batter to remaining prepared 8-inch cake pan; smooth top of batter with a spatula.
Step 5
Bake all 4 cakes in the preheated oven until a toothpick inserted into the center of each cake comes out clean about 30 minutes. Remove the cakes from oven and place onto cooling racks until cooled completely.
Step 6
Run a knife around edge of each cooled cake. Invert cakes remove pans and peel off parchment paper. Use a sharp knife to trim tops of cakes flat and even.
Step 7
Cut both of the red cake layers and the white cake layer in half horizontally. You will have 4 thin red cake layers and 2 thin white cake layers.
Step 8
Place a 4-inch round stencil on top of 1 thin red cake layer; cut out a 4-inch red cake round. Repeat placing stencil on 1 thin white cake layer to make 1 4-inch white cake round. Center the 4-inch round stencil on the blue cake; cut out and remove center portion covered by the stencil to make a blue cake ring.
Step 9
To assemble the cake you will need 2 thin 8-inch red cake layers 1 thin 8-inch white cake layer 1 4-inch thin red cake circle 1 4-inch thin white cake circle and 1 blue 8-inch cake ring. Reserve the leftover thin red cake layer and other cake pieces for making crumbs for decorating.
Step 9
To assemble cake place 1 8-inch thin red cake layer on a cake pan and frost the top generously with white frosting. Place the thin 8-inch white cake layer on top of the red one and frost the top. Place remaining 8-inch thin red cake layer atop the white one. Frost the red layer.