In a small pot, bring the cream to a boil. Pour the hot cream over the chocolate and let sit for 2 minutes without stirring. Whisk until smooth. Cover and refrigerate for 8 hours.
With the rack in the middle position, preheat the oven to 350°F (180°C). Butter two 8-inch (20 cm) springform pans with removable bottom and line 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 small bowl, whisk together the cocoa powder and coffee. Add to the egg mixture. Add the dry ingredients and stir until smooth. Spoon the batter into the prepared pans.
Bake for 45 to 50 minutes or until a toothpick inserted in the centre of a cake comes out clean. Let cool completely on a wire rack before unmoulding.
Meanwhile, line a baking sheet with a silicone mat or parchment paper.
In a bowl, combine all of the ingredients until just moistened. Press together with your hands and let fall onto the prepared baking sheet in varying sized clumps.
Bake for 8 to 10 minutes, stirring halfway through, or until cooked. Let cool completely.
Place the chocolate in a bowl.
In a small pot, bring the cream and corn syrup to a boil. Pour over the chocolate and let sit for 1 minute without stirring.
Whisk the ganache until smooth. Refrigerate for 1 hour or until thickened but still spreadable, stirring four or five times. Transfer the ganache into a pastry bag fitted with a plain tip.
Using an electric mixer, whip the milk chocolate whipped cream until firm peaks form but is still spreadable. Transfer ¼ cup (60 ml) of the cream into a pastry bag fitted with a plain tip.
Cut off the rounded top of each cake to make them as flat as possible. Cut each cake in half horizontally to get a total of 4 cake layers. With a spatula, spread the milk chocolate whipped cream evenly over the surface of each cake layer. Layer the four cakes and place on a serving dish.
Garnish the cake with small dollops of milk chocolate whipped cream, and ganache if desired. Sprinkle with the cocoa crumble. Cut into slices and serve with the remaining crumble, if desired.
This cake keeps well for up to 3 days at room temperature under a cake dome.
The remaining cocoa crumble is delicious as a topping for vanilla ice cream. It will keep for 10 days in an airtight container at room temperature.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.