Nonstick cooking spray
2 boxes white cake mix, plus ingredients called for on box
5 tsp. red gel food coloring, divided
1 c. mini dark chocolate chips
2 tbsp. all-purpose flour
3 c. (6 sticks) unsalted butter, softened
10 c. powdered sugar
1/2 c. whole milk (plus more as needed)
2 tbsp. vodka
2 tsp. green gel food coloring
2 tsp. yellow gel food coloring
A handful of black mini jelly beans
Step 1
Preheat oven to 350°. Line four 8” round cake pans with parchment paper and grease with cooking spray.
Step 2
Prepare cake mixes according to package instructions and add 4 teaspoons of the red gel food coloring to achieve a watermelon red color.
Step 3
Toss the chocolate chips with flour to coat and fold into the batter.
Step 4
Divide cake batter between prepared pans and bake according to package instructions or until a toothpick inserted into the center comes out clean, about 30 minutes. Let cakes cool in pans for 10 minutes, then invert onto wire racks to cool completely.
Step 5
Make frosting: In a large bowl using a hand mixer, beat butter and about half of the powdered sugar until smooth. Add the remaining powdered sugar, ½ cup of milk, and ¼ teaspoon salt and beat until fluffy. If the mixture is too stiff, add more milk.
Step 6
Divide frosting into two medium bowls. Leave one bowl of frosting white and stir in the remaining 1 teaspoon of red gel food coloring into the other bowl of frosting.
Step 7
Level the top of each cake to create even layers. Place a small dab of red frosting on the cake plate (to keep cake in place). Place down one cake and top with about ¾ cup red frosting, then top with second cake and repeat with the third and fourth layer.
Step 8
Scrape a heaping ½ cup of frosting in a pastry bag fitted with a 1-inch tip and pipe a ring around the outer edge of the cake. Using about a cup and a half of frosting, smooth a crumb coat around the outside of the cake. Transfer the cake to the refrigerator until the frosting is hardened, 1 hour.
Step 9
Spread the outside of the cake with the remaining white frosting. Fill in the top center of the cake with red frosting, being careful to keep the red frosting inside the piped white ring.
Step 10
Arrange jelly beans in the top red frosting, pressing them in gently to adhere.
Step 11
In 2 small bowls, mix 1 tablespoon vodka each with the green, light green and yellow gel food coloring. Using 2 separate sponges, blot the colors in vertical lines up the sides of the white frosting, creating a watermelon rind pattern.