Dark Chocolate Mousse Cake
Chocolate Cake
1-Preheat oven to 350ºF (180ºC): Preheat oven to 350ºF (180ºC). Grease and line a 9-inch (23cm) springform pan with parchment paper.
2-In a small mixing bowl, whisk together: In a small mixing bowl, whisk together the flour, Dutch cocoa powder, fine espresso powder, baking powder, baking soda, and salt.
3-In a large bowl and using a: In a large bowl and using a hand whisk, whisk together sugar, oil, sour cream, egg and vanilla until well combined.
4-Sift in the dry ingredients, ensuring the: Sift in the dry ingredients, ensuring the cocoa powder lumps are push through the sieve. Gently whisk the dry and wet ingredients together until nearly incorporated.
5-Add boiling hot water and gently whisk: Add boiling hot water and gently whisk until just combined. Do not overmix.
6-Pour cake batter into your prepared pan: Pour cake batter into your prepared pan and bake for 24 to 28 minutes or until an inserted toothpick comes out clean.
7-Cool on a wire rack for 15: Cool on a wire rack for 15 minutes, then remove the cake from the pan and let cool completely at room temperature or in the fridge.

Chocolate Mousse
8-In a small saucepan, and off heat,: In a small saucepan, and off heat, whisk together heavy cream, a whole egg, a yolk, sugar, cocoa powder, espresso powder, and salt until well combined.
9-Over low heat, and whisking constantly, heat: Over low heat, and whisking constantly, heat until the mixture reaches 170ºF (76ºC). It will take about 8 to 10 minutes.
10-Off heat, add chocolate and vanilla and: Off heat, add chocolate and vanilla and whisk until smooth and combined.
11-Transfer chocolate mixture to a medium bowl: Transfer chocolate mixture to a medium bowl and place a piece of plastic wrap directly on top to prevent a skin from forming. Chill the chocolate mousse mixture in the fridge for 1 to 1.5 hour, until thick and spreadable.
12-As the chocolate mousse is cooling, line: As the chocolate mousse is cooling, line the bottom of your springform pan with a fresh piece of parchment paper. If needed, level off the top of the cake with a serrated knife. Next, place cooled chocolate cake back into the springform pan. Wrap the sides of the cake with a 29-inch (74cm) long piece of acetate (cake collar). Tape the acetate together at the ends to prevent it from unraveling. You can also use parchment paper. Just lightly sprayed it with oil to make it easier to release the cake.
13-In a large mixing bowl, and using: In a large mixing bowl, and using a hand mixer, whip cold heavy cream until firm peaks. Do not overmix.
14-Then in 2 additions, gently fold the: Then in 2 additions, gently fold the chocolate mixture and whipped cream together until there are no more white streaks. Do not overmix.
15-Spread the chocolate mousse on top of: Spread the chocolate mousse on top of the cake layer. Chill for at least 8 hours.

Chocolate Ganache
16-When you’re ready to serve, make the: When you’re ready to serve, make the chocolate ganache. Place finely chopped chocolate from a bar or chocolate chips in a heatproof medium bowl.
17-In a small saucepan, and over medium: In a small saucepan, and over medium heat, bring heavy cream to a low simmer until it reaches about 185ºF (85ºC). Submerge hot cream over the chocolate and let stand untouched for 4 to 5 minutes.
18-Using a silicone spatula, slowly stir until: Using a silicone spatula, slowly stir until smooth and combined. If the chocolate hasn’t completely melted, place the bowl of ganache over a small pot of simmering water. Heat until completely smooth.
19-Remove the chilled cake from the fridge: Remove the chilled cake from the fridge and unmold it from the pan. Peel off the acetate/parchment paper and then slide the cake onto a serving plate.
20-Pour the chocolate ganache on top the: Pour the chocolate ganache on top the cake and using an offset spatula, spread it to the edges. Before serving, you can place the cake back into the fridge for 10 to 15 minutes to let the ganache set.