For the cake, preheat the oven to 350 degrees F. Spray (3) 9-inch round cake pans with non-stick cooking spray and line the bottoms with parchment paper.

In a large bowl, combine the flour, baking powder, baking soda and salt. In a stand mixer fitted with the paddle attachment, beat the butter until creamy, about 1 minute. Add the sugar and beat on high speed until pale and fluffy, about 3-4 minutes. On medium speed, beat in the eggs one at time, scraping down the bowl as needed, followed by the vanilla extract.

On low speed, mix in the dry ingredients in 3 additions alternating with the buttermilk until just combined. Divide the batter into the prepared baking pans, smoothing into an even layer. Bake for 25-27 minutes until a toothpick inserted in the center comes out clean. Cool the cakes in their pans on a wire rack.

For the frosting, place the dark chocolate in a heatproof bowl. In a small saucepan over medium, heat 3/4 cup heavy cream until it starts to bubble at the edges. Pour the cream over the dark chocolate. Let stand for 30 seconds before gently stirring until smooth. Cool to room temperature.

Place the milk chocolate in a heatproof bowl. In a small saucepan over medium, heat 1/2 cup heavy cream until it starts to bubble at the edges. Pour the cream over the milk chocolate. Let stand for 30 seconds before gently stirring until smooth. Cool to room temperature.

Place the white chocolate in a heatproof bowl. In a small saucepan over medium, heat 1/4 cup heavy cream until it starts to bubble at the edges. Pour the cream over the milk chocolate. Let stand for 30 seconds before gently stirring until smooth. Cool to room temperature.

When all the ganache has cooled, use an electric hand mixer, to beat each ganache until light and fluffy, about 2-3 minutes.

Place one cake on a turntable or cake stand and spread dark chocolate ganache across the top before adding another layer. Frost its top with milk chocolate ganache and top with the third layer. Use the white chocolate ganache to cover the entire cake in a thin crumb coat.

Frost the bottom third of the cake with the dark chocolate ganache. Then spread the milk chocolate ganache on the middle third. With the white chocolate ganache, frost the top of the cake down the sides to the milk chocolate ganache. Run a palette knife or offset spatula parallel to the cake around the frosting to blend the ganaches.