Classical French vinaigrette is a temporary emulsion of oil dispersed in vinegar, stabilised only by vigorous whisking and the viscosity of a quality mustard. The canonical ratio—three parts oil to one part vinegar—is a starting point, not a rule; the saucier adjusts acidity to complement the dish. Red wine vinegar yields assertive dressings for frisée aux lardons. Sherry vinegar brings nutty warmth to roasted beetroot. Champagne vinegar offers the delicacy required for a butter lettuce and chervil salad. Dijon mustard, added at the outset, acts as an emulsifier through its mucilage content, suspending oil droplets long enough to coat leaves evenly. The whisk technique matters: a rapid figure-eight in a bowl tilted at 30 degrees creates finer droplets than casual stirring. Season with fine sea salt dissolved in the vinegar first—salt dissolves poorly in oil. Freshly ground white pepper avoids the visual distraction of black specks on pale leaves. The finished vinaigrette should cling to a lettuce leaf without pooling, taste bright without puckering, and carry enough oil to give body without greasiness. A properly made vinaigrette separates within minutes; this is correct and expected. Whisk again at service. Temperature matters: a vinaigrette at 18°C coats better than one straight from refrigeration. For warm vinaigrettes, deglaze the sauté pan with vinegar, whisk in mustard off heat, then stream in oil—the residual fond adds depth no cold preparation can match.
3:1 oil-to-vinegar ratio as baseline, not dogma. Dissolve salt in acid before adding oil. Mustard emulsifies through mucilage, not lecithin. Whisk in figure-eight for finest droplet dispersion. Temporary emulsion — separation is correct, re-whisk at service.
Warm the bowl slightly for better initial emulsification. Taste the vinegar alone first — if it makes you wince, it will overpower the dressing. A drop of honey in a sherry vinaigrette bridges acidity without making it sweet. For service à la russe, dress the salad yourself; never send vinaigrette on the side in a fine dining context.
Adding salt to the oil phase where it cannot dissolve. Using blender speed which over-emulsifies into a thick paste. Refrigerating then serving cold — coats poorly below 15°C. Using balsamic as default — its sweetness overwhelms delicate greens.
Escoffier, Le Guide Culinaire; Saulnier, Le Répertoire de la Cuisine