10ounceshigh quality dark chocolate60-70%, coarsely chopped
1teaspoonpure vanilla extract
Preheat the oven to 350 degrees. Generously grease a 9 inch springform and line the bottom of the pan with parchment paper and butter the parchment.
Using a double broiler or microwave, melt the chocolate and set it aside to cool but not harden.
In the bowl of an electric mixer fixed with the paddle attachment, beat the butter and sugar together on high speed until pale, light and thoroughly combined, about 5 minutes.
Separate egg yolks and whites. I find it useful to use a three bowls for this using the third bowl to break the egg whites into to make sure no yolks get into the white before transferring each white into the egg white bowl. This just ensures that no egg yolks get into the final egg white bowl.
With the mixer on low speed, add the egg yolks one at a time, beating well after each addition. After all the egg yolks are added, scrape the bowl and beat a few more seconds. Add the cooled chocolate and mix until thoroughly combined. Scrape down the bowl, add the vanilla and coffee, and beat until just incorporated. Transfer this mixture to a separate bowl and clean the mixing bowl and whisk attachment well (if there is any leftover chocolate on the bowl the egg whites won't whip up). I use a lemon or apple cider vinegar to wipe down the bowl after cleaning it to make sure its ready top whip egg whites.
In the extra clean mixer, whisk the egg whites and salt until stiff peaks form. Scoop one cup of the egg whites into the chocolate mixture. Use a rubber spatula to gently fold in the egg whites. After about 30 seconds of folding, add the remaining egg whites and gently fold in until almost completely combined (or you can add the chocolate mixture slowly to the side of the egg white bowl and fold). Do not rush the folding process.
Pour into the prepared pan and use and offset spatular to smooth the top. Place a rectangular pan on the rack beneath with an inch or two of water inside to help the cake rise and be moist. Bake for 40-45 minutes or until the center barely giggles. Be careful not to over bake this cake.
Transfer to a wire rack and let cool completely. Use a knife to loosen the cake from the sides of the pan. Remove the springform sides.
To decorate with powdered sugar set a pattern or doily on top of the cooled cake, then dust with powdered sugar. Carefully remove your pattern. Slice and enjoy!
let cool in the oven (turned off) to prevent the middle from sinking.