Although modern curry-lovers might disdain the chip shop style of curry sauce, it is actually more-or-less identical to the receipt developed by the great Auguste Escoffier during his time at the London Ritz and published in his 'Modern Cookery' of 1903 (Escoffier 1903)
Original Receipt in the 'Guide to the Art of Modern Cookery ' by Auguste Escoffier (See: Escoffier);81 CURRY SAUCE
Slightly brown the following vegetables in butter: Twelve oz. of minced onions, one oz. of parsley roots, four oz. of minced celery, a small sprig of thyme, a bit of bay, and a little mace. Sprinkle with two oz. of flour and a teaspoonful of curry pepper.
Cook the flour for some minutes without letting it acquire any colour, and dilute with one and one-half pints of white stock. Boil, cook gently for three-quarters of an hour, and rub through a tammy. Now heat the sauce, remove its grease, and keep it in the bain-viarie. Serve this sauce with fish, shell-fish, poultry, and various egg-preparations.
N.B. This sauce is sometimes flavoured with cocoa-nut milk in the proportion of one-quarter of the diluent.