Triple Chocolate Ombré Cake

Ingredients

• triple chocolate cake layers
• 2 1/2 cups all-purpose flour (300g)
• 1 tsp salt
• 3 tsp baking powder
• 1/2 cup butter (113g)
• 1/2 cup oil (120ml)
• 1 cup granulated white sugar (200g)
• 2 large eggs
• 2 vanilla beans* (or 2 tsp vanilla extract)
• 1 cup buttermilk (240ml)
• 1/2 cup dark chocolate, melted and cooled (85g)
• 1/2 cup milk chocolate, melted and cooled (85g)
• 1/2 cup white chocolate, melted and cooled (85g)
• triple chocolate buttercream
• 1 1/2 cups butter, room temperature (339g)
• 3 cups powdered sugar (360g)
• 1/3 tsp salt
• 1/2 cup dark chocolate, melted and cooled (85g)
• 1/2 cup milk chocolate, melted and cooled (85g)
• 1/2 cup white chocolate, melted and cooled (85g)

Instructions

1. Preheat oven to 350°F / 175°C. Line the bottom and the sides of three 8" (20cm) baking pans with parchment paper. Lightly grease the sides of the pan with butter or oil that the paper sticks to the pan. Set aside.
2. In a medium bowl combine flour, salt, and baking powder and stir to combine. Set aside.
3. Make the triple chocolate cake layers: In a large mixing bowl with a stand or handheld mixer fitted with a whisk or paddle attachment, beat butter, oil, and sugar until creamy for about 2-3 minutes. Add eggs and vanilla and mix until fully incorporated. Alternately add dry ingredients and buttermilk, beginning and ending with dry ingredients. Stir just until combined. Divide batter into three bowls equally (use a kitchen scale for accurate results). Add dark chocolate to one batter and stir to combine. Transfer to one prepared baking pan. Repeat with milk and white chocolate.  Bake for 22-25 minutes or until a toothpick in the center comes out clean. Don't overbake or the cake will be dry. Let cool to room temperature.
4. Make the triple chocolate buttercream: Beat butter on medium-high speed until soft and creamy, about 2-3 minutes. Add powdered sugar and beat on medium-low speed until fully combined and smooth. Stir in salt to combine. Divide batter into three bowls equally (use a kitchen scale for accurate results). Add dark chocolate to one buttercream and stir until creamy. Repeat with milk and white chocolate. 
5. Assemble the cake: Cut a thin layer off the tops of your cakes to create a flat surface if needed. Place the dark chocolate cake layer on a cake stand, turner, or serving plate. Spread the dark chocolate buttercream evenly on top of the cake. Reserve about 1/4 for the sides. Place milk chocolate layer on top and spread with milk chocolate buttercream. Again, reserve about 1/4 for the sides. Repeat with the white chocolate layer. Frost the outside and the sides of the cake with the remaining frosting. For best results, spread one color after another around the sides with an offset spatula and level with the offset spatula in the end. Chill 4 hours in the fridge. Store leftovers in an airtight container in the fridge up to 2 days.