Cook the Book: Flourless Chocolate Cake

Position a rack in the lower third of the oven; preheat to 325°F. Meanwhile, to make the cake, line the bottom of the springform pan with parchment paper; grease the sides. Set pan on a wide sheet of heavy-duty foil; wrap foil up sides of pan without tearing it. Set pan in a larger baking pan or a roasting pan. Bring a kettle of water to a boil.

Preferably using a hand-held mixer, beat the eggs at high speed until volume of eggs doubles to about 1 quart, about 5 minutes. If you have to use a heavy-duty mixer, use the whisk attachment and speed 6 and beat to same volume, which will take about the same amount of time. Melt the chocolate and butter, with coffee or liqueur, if using. In a large heatproof bowl, either set in a pan of barely simmering water or in the microwave on medium (50 percent) power, stirring frequently for 4 to 6 minutes or until mixture is smooth and warm (about 115°F).

Fold one-third of egg foam into chocolate mixture with a large rubber spatula until just a few streaks of egg are still visible. Fold in half of the remaining foam in the same way. Fold remaining foam into batter until completely incorporated.

Scrape batter into prepared springform; smooth the surface. Set roasting pan on oven rack; pour enough boiling water into pan to come about halfway up the side of the springform.

Bake until the cake has risen slightly, the edges are just beginning to set, a thin glazed crust (like a brownie) has formed on the surface, and an instant-read thermometer inserted halfway into center of cake registers 140°F, 20 to 25 minutes.

Remove springform from water bath; set on a wire rack and let cool to room temperature. Cover and refrigerate overnight to mellow. Cake can be kept covered and refrigerated up to 4 days.

Puréed Raspberry Sauce

To make the sauce, if using frozen raspberries, drain them and reserve the juice.

Place fresh or drained frozen berries in the bowl of a food processor. Pulse briefly but not until perfectly smooth. Press the purée through a strainer to remove the seeds.

Add some of the reserved juice, if desired. If the purée seems too tart, sweeten it to taste. Cover and refrigerate until serving.

About 30 minutes before serving, remove the springform pan sides, invert the cake onto a sheet of waxed paper, peel off the parchment liner, and turn the cake right side up on a serving platter.

To serve, sieve the cake lightly with powdered sugar, if desired. Whip the cream with the vanilla and 2 teaspoons of sugar or more to taste until nearly stiff.

Serve slim slices on a pool of raspberry sauce with a dollop of whipped cream on top.