Preheat the oven to 350℉ (180℃). Butter and line a 9 inch spring form pan and set aside.

In a large microwaveable bowl melt the chocolate and butter together in 30 second intervals, stirring in between. (You can also do this over a bain-marie).

Allow the chocolate to cool slightly, then whisk in the sugar, egg yolks, one at a time, and vanilla extract.

Sift the cocoa powder and salt over the chocolate mixture and whisk to combine.

In the bowl of a stand mixer fitted with a whisk attachment (or using an electric hand mixer) whip the egg whites on medium-high speed until medium peaks form.

Mix in a large spoonful of the egg whites to the chocolate mixture to loosen it. Then gently fold in the rest of the egg whites until just combined, taking care not to deflate the batter.

Pour the batter into the prepared pan and smooth the top.

Bake for 40-45 min or until set around the edges but still jiggles in the center when shaken. Take care not to over bake or it won't be as moist. Allow to cool.

In a medium heat-proof bowl, add your chocolate and set aside.

In a small saucepan over medium-low heat (or in your microwave) heat the heavy cream until it reaches a simmer. Take it off the heat and pour it over the chocolate. Let the mixture sit for 3-4 minutes undisturbed. Then gently whisk until fully incorporated.

Drizzle the ganache over the cake and let it drip over the sides. Allow to set before slicing.

Enjoy with a cup of coffee! Store leftovers in an airtight container at room temperature for up to 3 days.