Flourless chocolate cake

Don't be intimidated by this protocol; the cake goes together quite quickly. If you have any questions about the protocol, ask Sean. There are no MSDS available for the reagents used, so use common sense and good hygiene.

Materials

• 8 large eggs, cold
• 1 pound (454 g) bittersweet chocolate, broken up (I used Trader Joe's Belgian Bittersweet Pound Plus bar--cheap and certainly adequate)
• 1/2 pound butter (227 g, 2 sticks), cut into ~1 cm³ chunks
• 1/4 cup (60 ml) Kahlua (optional; whiskey, rum, another liqueur, coffee, orange juice, or a smaller amount of extract like vanilla or almond would also be good)
• confectioner's sugar or cocoa powder for dusting (optional)
• H₂O, at or near boiling point

Equipment

• oven, preheated to 325°F
• 8" springform or other cake pan, bottom lined with parchment paper and sides greased (I used a 6 1/2" pan and 5/8 of the ingredients; you could also use a 9" pan, but reduce the baking time a few minutes and know the cake will be shorter)
• roasting pan or other larger vessel to serve as a water bath
• aluminum foil, wrapped underneath the cake pan to prevent water from leaking in
• wire cooling rack
• knife

Procedure

1. Beat eggs with hand-held mixer at high speed until volume doubles to approximately 1 quart, about 5 minutes. Alternately, beat in bowl of electric mixer fitted with wire whip attachment at medium speed (speed 6 on a KitchenAid) to achieve same result, about 5 minutes.
2. Meanwhile, melt chocolate and butter (adding coffee or liqueur, if using) in large heat-proof bowl set over pan of almost simmering water, until smooth and very warm (about 115°F on an instant-read thermometer), stirring occasionally to equilibrate. (For the microwave, melt chocolate and butter together at 50 percent power until smooth and warm, 4 to 6 minutes, stirring once or twice, much like melting agar.) Gently fold 1/3 of egg foam into chocolate mixture using large rubber spatula until only a few streaks of egg are visible; fold in half of remaining foam, then last of remaining foam, until mixture is totally homogenous. Be gentle because you want to preserve as much of that foam as possible since there's no other leavening agent.
3. Scrape batter into prepared cake pan and smooth surface with rubber spatula. Set roasting pan on oven rack and pour enough boiling water to come about halfway up side of springform pan. Bake until cake has risen slightly, edges are just beginning to set, a thin glazed crust (like a brownie) has formed on surface, and an instant read thermometer inserted halfway through center of cake registers 140 degrees, 22 to 25 minutes (it took mine more like 35 to reach that internal temperature, maybe due to the smaller pan making it thicker). Remove cake pan from water bath and set on wire rack; cool to room temperature. Cover and refrigerate overnight to mellow (can be covered and refrigerated for up to 4 days).
4. About 30 minutes before serving, remove springform pan sides, invert cake on sheet of waxed paper, peel off parchment pan liner, and turn cake right side up on serving platter. You can re-invert the cake, but the bottom will probably be smoother than the top. Sieve on confectioners’ sugar or unsweetened cocoa powder, if you like that sort of thing.

Adapted from Cook's Illustrated