_Parfait_ is the French word for "perfect," and these elegant little treats live up to the billing. Served straight from the freezer, their texture is similar to ice cream's, but they take on a mousselike consistency when thawed for a minute or two on the plate.
Whisk together yolks, remaining 1/4 cup sugar, and a pinch of salt in a metal bowl, then add hot caramel mixture in a slow stream, whisking. Transfer custard to saucepan. Cook custard over moderately low heat, stirring, until thickened and registers 170°F on thermometer (do not let boil).
04Pour custard through a fine-mesh sieve into bowl of standing mixer, then beat at high speed 10 minutes (mixture will be completely cool, thick, and pale). Beat in melted chocolate and vanilla.
05Whisk remaining cup cream in another bowl until it just holds stiff peaks, then whisk about one fourth of cream into chocolate mixture to lighten. Fold in remaining cream gently but thoroughly and divide mixture among paper cups, smoothing tops. Cover each cup with foil and freeze parfaits at least 12 hours.
06To serve, carefully tear off each paper cup and invert parfaits onto plates.