- 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 removable bottoms. Line the bottoms of both pans with parchment paper.
- In a bowl, combine the flour, baking soda, baking powder and salt. Set aside.
- In another bowl, whisk together the eggs, sugar, buttermilk, oil and vanilla.
- In a third bowl, whisk together the cocoa powder and water. Add to the egg mixture. Add the dry ingredients and mix until smooth. Divide the batter between the two prepared pans.
- Bake for 40 minutes or until a toothpick inserted in the centre of a cake comes out clean. Let cool completely on a wire rack. Unmould.
- Meanwhile, place the chocolate in a bowl.
- In a small pot, bring the cream and corn syrup to a boil. Pour over the chocolate. Let sit for 2 minutes without stirring.
- Whisk until the ganache is shiny and smooth. Add the butter. Refrigerate for 1 hour or until thickened but still spreadable, stirring 4 or 5 times.
- In a bowl, whisk the icing sugar and egg white with an electric mixer for 2 minutes. Add water as needed.
- Cut off the rounded tops of both cakes to make them as flat as possible. Cut each cake in half horizontally to have a total of 4 cake layers.
- Using a spatula, spread a thin layer of the ganache over the surface of each cake layer. Stack the 4 layers and transfer to a serving dish. Completely cover the outside of the cake with the remaining ganache. Refrigerate for 30 minutes before decorating.
- Using a small offset spatula, apply the royal icing to the bottom of the cake to look like snowbanks. Using a small brush, paint small pine trees. To add the falling snow effect, dip a toothbrush in the royal icing and run a finger or your thumb over the bristles to splatter the icing against the side of the cake, if desired. The cake will keep for 3 days, covered, at room temperature.
The cake freezes well without the royal icing