Serve cut into very small wedges with whipped cream and fresh raspberries or Fresh Berry Coulis. Please read About Flourless Chocolate Cakes.

Have all ingredients at room temperature, about 70°F. Preheat the oven to 325°F. Grease an 8 × 2-inch round cake pan (not a springform) and line the bottom with a round of parchment paper.

Combine in a large heatproof bowl:

Set the bowl over a large skillet of barely simmering water and stir often until the chocolate and butter are warm, melted, and smooth. Remove from the heat and whisk in:

Beat in large bowl, or in a stand mixer with the whisk attachment, on medium speed until soft peaks form:

Gradually add, beating on high speed until the peaks are stiff but not dry:

Use a silicone spatula to fold one-quarter of the egg whites into the chocolate mixture, then fold in the remaining whites. Scrape the batter into the pan and spread evenly. Set the pan in a large shallow baking dish or roasting pan, set the baking dish on a pulled-out oven rack, and pour in enough boiling water to reach halfway up the sides of the cake pan. Bake for exactly 30 minutes; the top of the cake will have a thin crust and the interior will still be gooey.

Set the cake pan on a rack to cool completely, then refrigerate until chilled, or overnight.

To unmold, slide a thin knife around the cake to detach it from the pan. Invert the cake and peel off the paper liner. Reinvert onto a serving platter. Sprinkle with:

Store in the refrigerator, but remove 1 hour or more before serving to soften. Cut with a hot knife, wiping off the knife between cuts.