Fish stock, roux, salt and pepper. Shell the langoustine. Soak the scallops in cold running water to clean. In a saute pan, heat the oil and butter, then saute shallots. Add langoustine, salt, pepper, and scallops. Saute quickly, they should be left slightly underdone; remove langoustine and scallops with slotted spoon and drain. Deglaze with lemon juice and vermouth. Add cream, fish veloute, salt and pepper and cook until the sauce is thick and smooth, whisking occasionally. Add julienned vegetables, langoustine, and scallops and cook very briefly until they are heated through. On individual serving plates, dish out three langoustine and one scallop. Pour sauce and julienned vegetables over the top and garnish with chopped parsley.