Bittersweet Chocolate Cloud Cake

1. Preheat oven to 350 degrees F and position rack in the center.
2. Pour 1/2 -inch water into a large roasting pan and place in oven. Butter the bottom and sides of a 9-inch springform pan. Line the bottom of the pan with a round of parchment paper, cut to fit. Butter the paper. Wrap the outside of the pan tightly with a large piece of heavy-duty aluminum foil.
3. Put 1 cup of sugar and the coffee in a medium saucepan over a high heat. Bring to boil, stirring occasionally to dissolve sugar. Remove from the heat add the chocolate and return to low heat. Keep stirring over heat until the chocolate is completely melted and the mixture is smooth. Remove from the heat and whisk in the cocoa powder and salt until smooth. Add brandy. Whisk in the egg yolks until no trace of yolk is left. Transfer the mixture to a large bowl and set aside to cool for 10 minutes. Whisk the flour into the chocolate mixture.
4. In the bowl of an electric mixer, beat the 6 egg whites with the cream of tartar on medium speed until soft peaks form. Gradually add the remaining 1/3 cup sugar and beat on high until peaks are almost stiff.
5. Stir about 1/4 of the egg whites into chocolate mixture (no need to fold at this point). Then gently fold in the remaining whites, 1/3 at a time, until no streaks of white remain. Pour into pan and smooth top. Bake in water bath for 35 minutes, until a toothpick inserted into center of cake comes out with a few moist crumbs clinging to it. Place cake on wire rack and let cool to room temperature. Remove sides of pan and carefully invert cake onto cardboard cake round or flat plate. Chill for at least 2 hours before glazing.
6. Remove the cake from the refrigerator and place it on a wire rack set over a baking sheet. Pour the chocolate glaze over the cake, covering it completely; spread evenly with a metal spatula. Serve the cake immediately or refrigerate. Bring the cake to room temperature before serving.

Chocolate glaze:

1. Put chocolate in a medium bowl. In a small saucepan, bring the heavy cream to a gentle boil. Whisk in the honey. Pour the hot cream mixture over the chocolate and let the mixture stand for 30 seconds to melt the chocolate. Whisk the mixture until smooth. Cover the surface of the glaze with plastic wrap and set aside at room temperature for 30 minutes, or until slightly thickened.