Farce mousseline is the most refined of all forcemeats — a velvet-smooth purée of lean protein (typically chicken breast, pike, or veal), egg white, and heavy cream, processed to a consistency so fine that the finished product melts on the tongue like a savoury cloud. The technique demands cold at every stage: the protein must be chilled to 0°C before processing, the bowl of the food processor should be nested in ice, and the cream must come straight from the refrigerator. Temperature control is not pedantry — it is physics. Above 4°C, the protein's myosin network loses its ability to emulsify fat, and the cream separates during cooking into oily pockets within a rubbery matrix. The lean protein is processed to a fine paste with salt (which extracts myosin and creates the binding network), then egg white is added for structure. The cream is incorporated in three stages, pulsing between additions, and the mixture is tested: a small quenelle poached in simmering water should be light, springy, and moist. If it is dense, add more cream. If it falls apart, reduce cream or add another white. The ratio — roughly 500g protein, 2 egg whites, 400ml cream, 10g salt — is a starting point that varies with the protein's leanness. Pike mousseline demands less cream than chicken. Veal sits between. The finished mousseline is used for quenelles de brochet, as the filling for vol-au-vent and ravioli, and as the inner layer of galantines and ballotines.
Everything cold — protein at 0°C, bowl on ice, cream from fridge. Salt extracts myosin, which creates the emulsion network. Add cream in three stages, test between additions. Poach a test quenelle: light and springy = correct; dense = more cream; falling apart = more white. Ratio: 500g protein, 2 whites, 400ml cream, 10g salt as baseline.
Freeze the food processor blade for 10 minutes before use — this keeps the temperature low during processing. If making pike mousseline, ensure every bone is removed before processing; even a tiny pin bone will catch in the tamis and tear it. For the lightest possible quenelle, fold a tablespoon of whipped cream into the finished mousseline just before shaping — this aerates the mixture without changing the binding structure.
Working with warm protein — the emulsion fails and the cream separates during cooking. Adding all the cream at once — the forcemeat cannot absorb it evenly. Skipping the test quenelle — you cannot assess texture by looking at raw forcemeat. Over-processing after cream addition — the heat from friction warms the mixture and breaks the emulsion.
Escoffier, Le Guide Culinaire; Larousse Gastronomique; The Professional Chef (CIA)