Step 1

Preheat the oven to 350F and grease the inside of a 9″ springform pan.

Step 2

Then 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

Now 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

Then whisk in the eggs and vanilla, followed by the sour cream.

Step 6

Dump in the dry ingredients and mix until it’s halfway combined. Then 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 either at room temperature or in the refrigerator.

Step 9

Once cooled, remove the ring from the pan and clean it off. Then 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

Now line the pan with a long sheet of acetate (AKA a cake collar), sliding it down between the cake and the sides of the pan. *See notes for parchment paper option

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

Now set the cake aside while we make 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. Then 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 you clean out the saucepan as we will be using it again.

Step 18

After a few minutes, whisk 3 egg yolks into the chocolate mixture one at a time. The chocolate will thicken significantly, but that’s ok.

Step 19

Now fill a tiny bowl with 3 tablespoons of water and sprinkle the gelatin on top. Let it sit while we heat the cream.

Step 20

Pour 3/4 cup of heavy cream into the cleaned saucepan and place it over medium-low heat. Heat just until it’s steaming but not bubbling.

Step 21

By now, the gelatin should have bloomed (AKA the powder has absorbed all the water and turned clear). 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. The chocolate mixture should now be smooth and glossy – almost like pudding.

Step 23

Now 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. Make sure both are spotless and completely dry.

Step 25

Now to that clean bowl, add the egg whites and cream of tartar. Whip on high speed. Once it starts to turns foamy and opaque, slowly whip in the fine sugar. Keep mixing on high speed until it turns white with soft peaks (pull the whisk away and if the meringue stands up with a little droop on the end, it’s perfect).

Step 26

Now we have our bowl of chocolate, a small bowl of whipped cream, and our large bowl of meringue (whipped egg whites + sugar).

Step 27

Using a rubber spatula, scoop the whipped cream into the chocolate mixture and gently fold to combine.

Step 28

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 also be somewhat thin and pourable.

Step 29

Pour the mousse over the chocolate cake and chill in the refrigerator for at least 4 hours but preferably overnight.

Step 30

When the mousse has set, release the ring from the pan and peel back the cake collar.

Step 31

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 32

Microwave the cream until it’s hot and bubbling. Pour the hot cream over the chocolate, ensuring the chocolate is completely submerged.

Step 33

Allow the mixture to sit for about 3 minutes, then whisk to combine.

Step 34

Pour the glossy ganache in the center of the cake and use a spoon or small overset spatula to spread it out towards the sides, allowing it to drip down.

Step 35

Chill the cake for at least 30 minutes to allow the ganache to set. Then slice and enjoy!