2. Melt the chocolate either in the microwave oven on high power at 30 second intervals, stirring between each interval, or in the top of a double boiler over gently simmering water. Take care not to burn the chocolate or let= water or steam get in it. Cool slightly.

3. In the bowl of an electric stand mixer fitted with the flat beater on high speed, beat the egg yolks until frothy, then reduce the speed to medium and gradually beat in the sugar until the mixture is very thick and light in color. On low speed mix the melted chocolate into the yolk mixture, then the flour.

4. Transfer the chocolate mixture to a large bowl. Wash the mixer bowl with hot, soapy water and dry it well. Place the egg whites and salt in the bowl and beat on high speed using the whisk attachment until the whites form stiff, but not dry peaks. Carefully fold the whites into the chocolate mixture until there are no white streaks showing. Pour the mixture into the prepared pan, spreading it evenly with a rubber scraper. Bake until the edges just begin to pull away from the sides of the pan, 15 to 17 minutes.

5. Set the pan on a wire rack, cover the top of the cake with a slightly damp kitchen towel and allow to cool to room temperature, at least one hour. Sift a layer of cocoa evenly over the top of the cake, then cover with two long overlapping strips of plastic wrap. Cover with another baking sheet and invert. Carefully peel off the parchment. Spread softened ice cream over the chocolate roll, leaving a 1 inch unfilled border around the edges and, using the plastic wrap underneath as a guide, roll the cake like a jelly roll. (Rolling from the long side gives an elegant slender roll that can be cut into 14 to 16 small slices. Rolling from the short side produces a shorter, fatter roll and bigger slices.) Slide seam down onto a board or platter. Wrap in the plastic wrap and a layer of aluminum foil and freeze for several hours.

6. To serve, use a sharp serrated knife to slice the cake into 1 1/2 inch thick slices and top with hot fudge sauce and whipped cream.

Notes from author: This is the birthday cake of choice in our household. I love it because it can be made weeks in advance and frozen. Don't panic if the cake splits and cracks while it's being rolled...any blemishes can be artfully disguised with chocolate sauce and whipped cream.