• 6 1/2 oz best-quality semisweet chocolate; chopped
  • 3/4 c unsalted butter; plus 1 tb
  • 3 egg yolks
  • 1 egg
  • 1 c sugar; plus more for dusting pan
  • 6 egg whites
  • Cocoa powder or confectioner's sugar; for dusting
1. Heat oven to 300 degrees. Grease a 10-inch springform pan with one tablespoon butter, and dust generously with granulated sugar.

2. Melt chocolate and butter over simmering water in a double boiler, until melted about 6-8 minutes. Remove from heat and set aside to cool.

3. In an electric mixer fitted with whisk attachment, whip the yolks and whole egg with 2/3 cup sugar on a high speed, until it is pale yellow and falls in a thick ribbon when the beater is raised, about 5 minutes. Scrape down the sides of the bowl once or twice during mixing. Set aside.

4. In an electric mixer, using a second whisk attachment and bowl, whip the egg whites with remaining 1/3 cup sugar on high speed until thick and foamy, about 3-4 minutes. Set aside. (The mixing bowl and whisk attachment must be clean and free of grease.) While the whites are beating, slowly add the cooled melted chocolate slowly to the yolk mixture.

5. Temper the whipped egg whites by mixing in a small amount of the chocolate mixture, about 1/4 cup. Then gently fold the whites into the chocolate yolk mixture, working quickly as to not loose the volume of the whites; the mixture will have a slightly marbleized appearance.

6. Pour the batter into the prepared pan and place on a parchment- lined baking sheet. Place in heated oven, and bake for 50 to 60 minutes. Remove from oven and allow to cool in the pan on a cooling rack. When completely cool, gently run a knife around the edges of the pan and release spring. Dust with cocoa powder or confectioner's sugar before serving.