Flourless Chocolate Cake

Place rack in center of oven; preheat oven to 375°F. Butter an 8-inch round cake pan, line bottom of pan with a round of parchment paper, and butter paper.

Melt ½ cup (4 oz.) fine-quality bittersweet chocolate, chopped and 8 Tbsp. (1 stick) unsalted butter in a double boiler or heatproof bowl set over a saucepan of barely simmering water (do not let mixing bowl touch water), stirring occasionally until smooth.

Remove from heat and whisk in ¾ cup (150 g) sugar to combine. Add 3 large eggs and whisk until no streaks remain. Sift ½ cup (42 g) unsweetened cocoa powder over chocolate mixture and whisk until just combined. Pour cake batter into prepared pan and bake until top has formed a thin crust, about 25 minutes. Cool cake in pan on a wire rack 5 minutes, then invert onto a serving plate.

Sift additional cocoa powder on top of cake and serve with sorbet if desired. Do ahead: Cake can be baked 1 week ahead (let cake cool completely, then store in an airtight container at room temperature).