This is on my Chocolate bindge. Make 16 slices instead of 8.

8 ounces bittersweet chocolate (preferably 62% + cocoa), finely chopped
12 ounces (3 sticks) unsalted butter, cut into pieces (yes it is a lot, but you only need a small slice)
1 cup sugar
1/2 cup brewed coffee (I can't have this, so I did water, OJ may work)
6 large eggs
1 tsp vanilla extract
1/8 tsp salt

Preheat oven to 350 F. Butter the bottom and sides of a 9-inch round cake pan. Line the bottom with a parchment round and butter the parchment. (If you’re using a pan with a removable bottom like a springform, make sure to wrap the pan with 2 or 3 layers of foil, so it doesn't drip out.)

Place chopped chocolate in a bowl.

In a saucepan over medium-high heat, stir butter, sugar and coffee until the butter is melted and mixture is boiling. Pour the hot mixture over your chopped chocolate. Let stand for 1 minute then gently stir until chocolate is melted and the mixture is smooth.

In a medium bowl, whisk the eggs vigorously until blended. Whisk in the vanilla and salt. Cool for a few min. Slowly add about 1/2 cup at a time (2 or 3 depending on how cool) hot chocolate mixture to the eggs, whisking constantly. (Tempering the eggs with a little bit of the hot chocolate mixture will prevent scrambled eggs when combining the two mixtures.) Add the egg mixture to the hot chocolate mixture and whisk to combine well.

Strain the batter through a sieve (to catch any cooked egg bits) and then pour batter into prepared pan (I just strained it into the pan). Set cake pan in a larger pan and fill the pan with enough hot water to come halfway up the sides of the cake pan. Bake for 35-45 minutes, until the center is shiny and set but still a bit jiggly. Transfer cake pan to a cooling rack and cool for 20 minutes.

Run a thin knife around the edge of the pan to loosen the cake. Place a cardboard round on top of the pan and invert the cake onto it. (I lightly greased a plate to invert it on) Remove pan and carefully remove the parchment paper. Refrigerate the cake for at least 2 hours before glazing with chocolate glaze (over night is best).

Ganache
6 ounces bittersweet chocolate, finely chopped
2/3 cup heavy whipping cream
1 tsp vanilla extract

Place chopped chocolate in a medium bowl.
In a small saucepan, bring the cream to a boil. Remove pan from heat and add the chopped chocolate. Let stand for 1 minute then gently stir until chocolate is melted and the glaze is smooth. Gently stir in the vanilla. Transfer glaze to a small bowl and cover the surface of the glaze with plastic wrap and let cool to room temperature before using.

To glaze the cake:

Place the chilled cake, on a wire rack set over a baking sheet. Slowly pour the warm glaze onto the center of the cake. Smooth the glaze over the top and sides, letting the excess drip onto the baking sheet.

Scrape the extra glaze from the baking sheet and put it in a small ziploc bag. Seal the bag and cut a tiny hole in one of the bottom corners. Gently squeeze the bag over the top of the cake to drizzle the glaze in a decorative pattern. Refrigerate the cake at least one hour before serving.