Combine egg yolks and sugar in the top of a double boiler, over boiling water. Reduce heat to low, and cook for about 10 minutes, stirring constantly. Remove from heat. In the bowl of an electric mixer, whip yolks until thick and lemon-colored. Add mascarpone to whipped yolks, beat until combined. In a separate bowl, whip cream to stiff peaks. Gently fold whipped cream in the Mascarpone mixture; set aside. Dip each ladyfinger into the espresso just long enough to get them wet; do not soak them. Arrange ladyfingers in the bottom of a 9-inch square baking dish. Spoon half the mascarpone cream filling over the ladyfingers. Repeat process with another layer of ladyfingers. Add another layer of tiramisu cream and refrigerate 4 hours or overnight. Dust with cocoa before serving. Makes 18 servings.
Tip: When Mascarpone cheese is unavailable, you may substitute 8 ounces full fat cream cheese, 1/4 cup whipping cream and 2 tablespoons softened unsalted butter; whip until just blended. This will give the equivalent of around 1 1/4 cups mascarpone.
Approximate Nutrient Analysis per serving (based on 18 servings):
360 calories, 27 g fat, 15 g saturated fat, 180 mg cholesterol, 65 mg sodium, 26 g carbohydrate, 1 g fiber, 11 g sugar, 6 g protein