This recipe is from Bon Appetit. It is truly "Death by Chocolate." It's a rich and moist flourless cake. Next time, I will try adding less corn syrup to the glaze. It makes the glaze cloyingly sweet.
Butter 9-inch-diameter springform pan. Line bottom of pan with parchment paper and butter the paper. Wrap outside of pan with foil.
Stir chocolate and butter in medium saucepan over low heat until melted and smooth. Remove from heat. Cool to lukewarm, stirring often.
Beat egg yolks and 6 tablespoons sugar in large bowl until mixture is thick and pale, about 3 minutes if you use an electric mixer.
Fold chocolate mixture and vanilla extract into yolk mixture.
Using clean dry beaters, beat egg whites in another large bowl until soft peaks form. Gradually add remaining 6 tablespoons sugar, beating until medium-firm peaks form. Fold whites into chocolate mixture in 3 additions. Pour batter into prepared pan.
Bake about 50 minutes or until cake top is puffed and cracked and tester inserted into center comes out with some moist crumbs attached, about 50 minutes. Cool cake in pan on rack. Don't worry if the cake falls.
Cut around pan sides to loosen cake and then remove pan sides. Invert cake onto a plate. Peel off parchment paper.
For the glaze: Bring cream and corn syrup to simmer in medium saucepan. Remove from heat. Add chocolate and whisk until melted and smooth.
To finish: Spread 1/2 cup glaze smoothly over top and sides of cake. Freeze until almost set, about 3 minutes.
Pour remaining glaze over cake; smooth sides and top. Place cake on platter. Chill until glaze is firm, about 1 hour. Serve at room temperature.