Preparation Inline ingredients (beta)
Cook mode
Step 1 Preheat the oven to 350F and grease the inside of a 9″ springform pan.
Step 2 Remove the ring, lay a sheet of parchment paper on the bottom plate, and close the ring on top. Some paper will be sticking out of the sides.
Step 3 In a medium bowl, whisk together the flour, cornstarch, cocoa powder, baking soda, baking powder, and salt. Set aside.
Step 4 In a large mixing bowl, whisk together the sugar, dark brown sugar, and oil. It should look like wet sand.
Step 5 Whisk in the eggs and vanilla, followed by the sour cream.
Step 6 Dump in the dry ingredients and mix until halfway combined. Pour in the hot coffee and mix until smooth. The batter will be very thin.
Step 7 Pour the batter in the prepared pan and bake for 25-30 minutes or until a toothpick in the center comes out clean with a few moist crumbs.
Step 8 Allow the cake to cool completely at room temperature or in the refrigerator.
Step 9 Once cooled, remove the ring from the pan and clean it off. Level off the top of the cake using a cake leveler or a large knife.
Step 10 Place the clean ring back on the pan with the cake still inside.
Step 11 Line the pan with a long sheet of acetate (cake collar), sliding it down between the cake and the sides of the pan.
Step 12 Stir together the hot coffee and cocoa powder.
Step 13 Spoon the mixture over the cake, evenly soaking the entire surface.
Step 14 Set the cake aside while making the mousse.
Step 15 Add the chopped chocolate to a heat-safe bowl.
Step 16 Fill a saucepan with about 1/2 inch of water and place over medium heat. Place the heat-safe bowl on top, ensuring it does not touch the water.
Step 17 Once simmering, the water below will slowly melt the chocolate. Stir until smooth then remove from heat. Allow the chocolate to cool slightly while cleaning the saucepan.
Step 18 After a few minutes, whisk 3 egg yolks into the chocolate mixture one at a time. The chocolate will thicken significantly.
Step 19 Fill a tiny bowl with 3 tablespoons of water and sprinkle the gelatin on top. Let it sit while heating the cream.
Step 20 Pour 3/4 cup of heavy cream into the cleaned saucepan and place it over medium-low heat. Heat until steaming but not bubbling.
Step 21 Scoop the gelatin into the steaming cream and whisk to melt.
Step 22 Remove from heat and pour half of the cream into the chocolate and egg yolk mixture. Whisk until smooth, then whisk in the rest of the hot cream.
Step 23 In a large bowl using a hand or stand mixer with the whisk attachment, add the remaining 1 cup of heavy cream. Whip on high speed until light and fluffy with stiff peaks.
Step 24 Scoop the heavy cream into a smaller bowl and clean out the big mixing bowl and whisk.
Step 25 In the clean bowl, add the egg whites and cream of tartar. Whip on high speed. Once it starts to turn foamy and opaque, slowly whip in the fine sugar. Mix on high speed until it turns white with soft peaks.
Step 26 Using a rubber spatula, scoop the whipped cream into the chocolate mixture and gently fold to combine.
Step 27 When it's well incorporated, scoop in the meringue and repeat the process. Keep folding until the mousse is all one color with zero white streaks. The mousse should be somewhat thin and pourable.
Step 28 Pour the mousse over the chocolate cake and chill in the refrigerator for at least 4 hours but preferably overnight.
Step 29 When the mousse has set, release the ring from the pan and peel back the cake collar.
Step 30 For the ganache, add the chopped chocolate to a medium-sized heat-safe bowl and the heavy cream to a heat-safe measuring glass.
Step 31 Microwave the cream until it's hot and bubbling. Pour the hot cream over the chocolate, ensuring the chocolate is completely submerged.
Step 32 Allow the mixture to sit for about 3 minutes, then whisk to combine.
Step 33 Pour the glossy ganache in the center of the cake and use a spoon or small offset spatula to spread it out towards the sides, allowing it to drip down.
Step 34 Chill the cake for at least 30 minutes to allow the ganache to set. Slice and enjoy!
