Dark Chocolate Ganache
- With the rack in the middle position, preheat the oven to 350°F (180°C). Butter the sides of two 8-inch (20 cm) springform pans with removeable bottoms. Line the bottoms with parchment paper.
- In a bowl, combine the flour, cocoa powder, baking soda and baking powder.
- In another bowl, whisk together the eggs, sugar, oil and vanilla. Add the dry ingredients alternating with the buttermilk. Mix until smooth. Divide the cake batter between the prepared cake pans.
- Bake for 40 to 45 minutes or until a toothpick inserted in the centre of the cakes comes out clean. Let cool. Unmould and let cool completely on a wire rack, about 3 hours.
Dark Chocolate Ganache
- Place the chocolate in a bowl.
- In a small pot, bring the cream and corn syrup to a boil. Remove from the heat and pour over the chocolate. Let sit for 1 minute without stirring. Whisk until smooth. Add the butter. Cover and refrigerate for 30 minutes or until chilled but still spreadable. Reheat slightly in the microwave oven as needed before using.
- In a bowl placed over a pot of simmering water, heat the sugar and egg whites, stirring constantly, until the sugar has dissolved. Remove the bowl from the pot. Whisk with an electric mixer until stiff peaks form. The mixture should be lukewarm. Add the vanilla.
- Add one or two pieces of butter at a time while whisking constantly. Continue to whisk for 5 minutes until the mixture is light and creamy (see note). Using a spatula, scrape down the sides and bottom of the bowl a few times (see note).
- Cut off the rounded tops of the cooled cakes to make them as flat as possible. Cut each cake in half horizontally to have a total of 4 cake layers. On a serving dish, place one cake layer and cover with one-third of the ganache. Repeat this step by stacking two more cake layers and covering each with ganache. Top with the last cake layer with no ganache.
- Place ⅓ cup (75 ml) of the vanilla icing in a bowl. Add enough black food colouring to get a very dark icing.
- Place half of the remaining icing in a bowl. Divide what is left between two other bowls. Add blue food colouring to one of the bowls. Add more blue colouring to the remaining two bowls to obtain three different shades of blue (the darkest shade of blue should be the bowl with the largest amount of icing).
- Using a large offset spatula, spread the darkest blue icing evenly over the top of the cake. Continue down the side to cover the top third of the cake all the way around with a strip of dark blue icing.
- Spread the lighter blue icing around the middle of the cake in a strip as wide as the dark blue strip above. Finish with a strip of the lightest blue around the bottom third of the cake. Refrigerate for 1 hour.
- Meanwhile, draw the outline of a city skyline along the length of the strip of parchment paper. Cut out the skyline and remove the bottom of the strip.
- Place the stencil around the bottom of the cake and press lightly to adhere. Using a small offset spatula, apply a thin layer of black icing to fill in the stencil of the skyline. Gently remove the stencil.
- Place the silhouette of the skateboarder and on the top of the cake. The cake will keep for 3 days, covered, at room temperature.
To avoid wasting the egg yolks, use liquid egg whites. An egg white weighs 30 g and measures 2 tbsp (30 ml). Therefore, you will need 1/2 cup (120 g) egg whites for this recipe.
The mixture may separate after you add about half of the butter. Everything should come together once you add the remaining butter. This step takes time, so don’t add the butter too quickly. If the icing seems too soft when you are ready to apply it to your cake, refrigerate it for a few minutes, then whisk it up again.
The icing can be prepared in advance if left covered at room temperature. Mix the icing well before applying it to your cake.