Preheat oven to 350°.

Bring 1/2 cup water to a boil in a small saucepan. Add cocoa and espresso, stirring until smooth. Remove pan from heat. Add chocolates; gently stir until mixture is smooth. Stir in brandy and vanilla. Pour chocolate mixture into a large bowl. Let stand 10 minutes; stir occasionally.

Combine eggs, egg whites, sugar, and salt in the top of a double boiler, stirring with a whisk. Cook over simmering water until a thermometer reaches 115° (about 2 minutes), stirring constantly with a whisk. Place egg mixture in a medium bowl; beat with a mixer at high speed until ribbony, soft peaks form (about 5 minutes).

Gently stir one-third of egg mixture into chocolate mixture; gently fold in remaining egg mixture. Gently fold in whipped topping. Spoon batter into an 8-inch springform pan coated with baking spray, spreading evenly. Bake at 350° for 27 minutes or until almost set (center will not be firm but will set as it chills). Cool to room temperature on a wire rack.

Cover and chill at least 8 hours or overnight.