SCALLOP AND SOLE MOUSSELINES

Steps:

• 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.