White Chocolate Rainbow Cake

Ingredients

• 1 cup unsalted butter, at room temperature, plus extra for greasing
• 2 1/4 cups all-purpose flour
• 1/3 cup cornstarch
• 4 1/2 tsp. baking powder
• 1/2 tsp. salt
• 2 cups superfine sugar
• 2 tsp. vanilla extract
• 4 medium eggs, separated
• 1 1/4 cups whole milk
• Gel food coloring in red, yellow, orange, purple, blue, and green

For the white chocolate Italian meringue frosting:

• 5 1/2 ounces white chocolate
• 1 1/2 cups superfine sugar
• 6 medium egg whites
• 2 cups + 6 Tbsp. unsalted butter, at room temperature

Directions

Pour the egg whites into a clean, grease-free bowl and whisk until they hold soft peaks. Add the whites to the cake batter and gently fold together until just combined and there are no streaks of white. Divide the batter equally between six small bowls. Add a small amount of each coloring to each bowl, enough to make it a vibrant color. Add the first three bowls to the prepared pans and bake for 15 minutes or until they spring back when lightly touched. Let cool in the pans for 10 minutes before turning onto a wire rack to cool completely. Repeat with the remaining three portions of batter.

To make the frosting, melt the chocolate in a heatproof bowl set over a pan of gently simmering water, making sure the bottom of the bowl doesn’t touch the water. Remove from the heat and let cool.

To assemble the cake, put the purple cake layer on a cardboard cake board or serving plate and top with a thin layer of frosting. Repeat the process with the other cake layers in the order of a rainbow (purple, blue, green, yellow, orange, red) and then spread the remaining frosting across the top and sides of the cake.