Step 1

Preheat the oven to 300 degrees F.

Step 2

Grease a 9-inch springform pan and then line with parchment paper (the bottom and sides). Grease the paper as well, then dust with cocoa powder.

Step 3

In the top of a double boiler over lightly simmering water, melt chocolate and butter. Remove from heat, and stir in sugar, cocoa powder, eggs, and vanilla. Pour into prepared pan.

Step 4

Bake for 30 minutes. Remove from oven and use the back of a spoon to smush the cake down to make a thinner crust. Let cool to room temperature before adding the cheesecake mixture.

Step 5

Preheat the oven to 325 degrees F.

Step 6

In a large mixer bowl, beat cream cheese and sugar until light and fluffy. Add eggs one at a time while beating. Stir in sour cream, vanilla, and Bailey's or coffee. Stir in the melted chocolate.

Step 7

Pour mixture over crust. Bake for about 1 1/2 hours, until the center is raised and set. Let cool to room temperature. Proceed to mousse step or cover cake with aluminum foil and refrigerate until the next day.

Step 8

Place the chocolate in a large bowl set over low simmering water (or in the top of a double boiler). Stir chocolate until melted. Turn off the heat and let stand to reach room temperature.

Step 9

Beat the cream over ice until it forms soft peaks. Set aside and hold at room temperature. With a mixer, whip egg to soft peaks. Gradually add the sugar and continue whipping until firm.

Step 10

Transfer the chocolate to a large bowl. Using a spatula, fold the egg whites into the chocolate. When the eggs whites are almost completely incorporated, fold in the whipped cream.

Step 11

Add mousse on top of cheesecake and smooth top. Cover cake with foil and refrigerate until ready to top with ganache.

Step 12

Melt the chocolate in the top of a double boiler, in a bowl on top of simmering water, or in the microwave at 50% power in 30-second intervals.

Step 13

Boil the cream, then pour over the melted chocolate. Whisk until smooth. It will come together, just keep whisking. Add the corn syrup and mix completely.

Step 14

Allow to cool briefly. Do not allow the ganache cool too much or it will start to harden when it hits the cold mousse and be harder to spread. If you'd like the ganache to drip down the sides of the cheesecake, remove the springform pan sides and place cake on a platter lined with wax paper (the wax paper just needs to cover the bottom edges of the cake).

Step 15

Spread the ganache over mousse layer, allowing to drip down sides if desired. Sprinkle with cocoa powder if desired. Cover cake with aluminum foil and chill.