Preheat your oven to 350°F (175°C) and prepare two 9-inch round cake pans by greasing them and lining with parchment paper.

In a large bowl, whisk together all-purpose flour, granulated sugar, baking soda, salt, and cocoa powder until combined and fluffy.

In a separate bowl, blend vegetable oil, buttermilk, eggs, white vinegar, vanilla extract, and food colorings until smooth.

Pour the wet ingredients into the dry ingredients and gently fold until just combined.

Divide the batter between the cake pans and bake for 25-30 minutes, or until a toothpick comes out clean.

Let the cakes cool in the pans for about 10 minutes, then turn them out onto a wire rack.

To make the frosting, melt white chocolate. Beat cream cheese and unsalted butter until fluffy, then gradually add confectioners' sugar, folding in the melted chocolate.

Assemble the cake by placing one layer on a plate, spreading frosting on top, then placing the second layer on and covering the whole cake.

Chill the assembled cake for at least 30 minutes before serving.