Preheat oven to 350°F / 175°C. Line four 7" or four 6" pans with parchment rounds and grease with non-stick baking spray or homemade cake pan release.
Mix 3 cups all-purpose flour, 3 cups Domino® Light Brown Sugar, 2 1/2 tsp baking powder and 1 tsp salt together in a stand mixer with a paddle attachment or hand mixer until fully combined.
Mix in 1 cup of room temperature, unsalted butter slowly into the dry ingredients on a low speed. Continue to mix until no large chunks of butter remain, and the mixture looks like moist sand.
Pour in 1 cup of egg whites and mix on low until just incorporated. Scrape the sides and bottom of the bowl as needed with a rubber spatula.Then mix in 1 1/2 cups sour cream, 2 Tbsp of vegetable oil, and 1 Tbsp of vanilla on a low speed until fully incorporated.
Scrape down the sides of the bowl with a rubber spatula one more time, then beat on a medium speed for about 30 seconds to make sure everything is properly mixed together. This also helps lighten the texture of the cake layers.
Divide the batter evenly between four bowls (about 450 grams of batter per bowl). Create yellow, pink, blue, and purple batter using a squirt of gel food coloring. Mix by hand with a spatula until the batter is evenly colored.
Pour each color into one of the prepared cake pans. Bake for 33-36 minutes or until a toothpick comes out clean. Let the pans cool for 10 minutes, then run an offset spatula around the perimeter of the pan to separate the cake from the pan.
Place cake layers into the freezer for 45 minutes to accelerate the cooling process. Once the layers are fully cooled, carefully flip the pans, and remove the layers from the pans. If you make these cake layers in advance and freeze them, let them thaw for about 20 minutes before making the cake. The cake layers should still be slightly cold to the touch, which will make it easier to assemble the cake.
Use a serrated knife to level the tops of the layers. Then use a 6", 4" and 2" circle cutter to carefully cut each layer into four rings. Carefully reassemble the layers, following the same color pattern (pink, purple, yellow, blue). Set aside.
While the cake layers bake and cool, make the vanilla buttercream frosting.
In the bowl of a stand mixer or a large bowl, beat 2 cups of unsalted butter on a medium speed for 30 seconds with a stand mixer and paddle attachment or hand mixer until smooth.
Mix in 1 Tbsp of vanilla extract and 1/2 tsp salt on a low speed. Gradually mix in 7 cups of Domino® Powdered Sugar and 1/3 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 in additional cream (1 Tbsp at a time). If the frosting seems too thin, add in more Domino® Powdered Sugar (quarter of a cup at a time).
Cover the buttercream flush with plastic wrap to prevent crusting, then set aside.
Stack and frost the checkerboard cake layers on a greaseproof cake board or flat plate using a dab of frosting to help stick the first cake layer to the board. Keep the color order in mind as you stack the layers to make sure the checkerboard is aligned properly. Start with the pink layer on the outer edge, then add the purple, yellow, and blue layer.
Spread an even layer of buttercream between each cake layer with a large offset spatula. Place the top cake layer upside down to make it easier to frost and create sharp corners.
Add a thin coat of frosting around the cake to fully cover the cake layers. Smooth using a bench scraper, then chill the cake in the fridge (30 minutes) or freezer (10 minutes) until the frosting is firm to the touch.
While the crumb coat chills, heat 1/3 cup of heavy cream in a heat-proof bowl in the microwave for 45 seconds, or until it's just beginning to bubble. Gently pour 1 cup of white chocolate chips into the heavy cream. Make sure they are fully covered with cream. Let mixture sit for 1 minute.
Stir slowly until the cream and white chocolate are combined and smooth. If any bits of chocolate aren't fully melted yet, heat the mixture again for 20 seconds and stir. Repeat as needed until the chocolate is fully melted.
Divide the ganache evenly between four small bowls. Use gel food coloring to make pink, purple, yellow, and blue ganache. Let the ganache cool until it reaches the desired viscosity (barely warm to the touch).
Place plastic wrap over the bowls to prevent the ganache from forming a skin.
Decorating This Peeps Drip Cake:
Add a second, thicker layer of frosting to the cake, and smooth using a bench scraper. Place the cake in the freezer to chill for 10-15 minutes, or in the fridge for 30 minutes.
Once the frosting is firm to the touch, use a plastic squirt bottle or a spoon to add the drips to the cake. Add the drips in color blocks, with 4-5 drips per section.
Then decorate the top of the cake with a ring of different colored peeps and your favorite Easter candies.