9 ounces bittersweet chocolate, chopped
8 tablespoons unsalted butter
1/3 cup sugar
4 large eggs at room temperature, separated
2 tablespoons flour
pinch of salt
Heat oven to 350. butter a 9-inch loaf pan and line bottom with a strip of parchment paper.
In a large bowl over simmering water, heat chocolate and butter together until just melted and smooth.
Remove from heat and stir in half the sugar, then the egg yolks, the the flour.
whip the egg whites with salt until the form soft, droopy peaks. Gradually whip in remaining sugar until the whites are smooth and hold their shape when the whisk is lifted.
Use a rubber spatula to fold one third of the egg whites into the chocolate mixture to lighten it, then fold in remaining egg whites until mixture is smooth and no white streaks remain.
Scape batter into laof pan, smooth top, and bake 35 minutes until cake feels slightly firm in the center. Do not overbake.
Cool in pan before serving.
Cake can be stored for three days, or frozen, well wrapped in plastic, for up to one month.
From David Lebovitz.