Scallop and Sole Mousselines

Rinse scallops and sole and pat dry, then purée in a food processor until very smooth. Force purée through a fine-mesh sieve into a metal bowl, scraping bottom of sieve as needed.

Set metal bowl in a larger bowl of ice and cold water, then add egg white to purée and stir vigorously with a wooden spoon or rubber spatula until well combined. Add cream 2 tablespoons at a time, stirring after each addition until incorporated. (Mousseline should be the consistency of soft mashed potatoes; if it becomes runny or separates, stop adding cream and chill mixture, covered — still in ice bath — until firmer, about 30 minutes. Then continue adding cream.) Cover bowl and chill mixture 8 hours.

Put oven rack in middle position and preheat oven to 350°F.

Cut out 10 rounds of parchment paper to line bottoms of molds and 10 rounds to line tops of molds, using 1 timbale mold as a guide. Brush molds with some melted butter and line bottom of each with a round of parchment. Chill molds 5 minutes (to set butter), then brush paper and sides of molds again with more melted butter.

Stir salt, pepper, nutmeg, chives, and dill into mousseline, then divide among molds (they will be about two-thirds full). Rap molds on counter once or twice to settle mixture, then put a buttered parchment round, buttered side down, on surface of each mousseline. Put molds in an 8-inch square or round baking pan (2 inches deep) and bake in a hot water bath in oven until mousselines are just set and springy to the touch, 20 to 25 minutes.

Cool mousselines in molds on a rack until warm, about 10 minutes, then invert onto a large plate and pat dry with paper towels before transferring to soup bowls.