Hot Hazelnut and Parsley Vinaigrette

This is an excellent method for finishing the cooking liquids from roast meats or braised fish and fish fillets cooked en sauce (see “Braising,”). The sauce, which is bound and flavored with parsley, can be flavored with different oils, vinegars, lemon or lime juice, verjuice, or herbs. Because the sauce is unstable and its flavor fragile, serve it immediately after blending. Fish and meats can be lightly brushed with this sauce, or they can be sur