From 1912:
This famous soup is made in the imperial kitchen. The ingredients and process being somewhat elaborate, a special room called the “olio kitchen” is used for its preparation.
Take seven pounds of beef and six pounds of veal and cut them into small pieces; lay side by side in a deep pan, and upon this place a thin layer of sliced suet, and upon the top of that four onions cut in slices. Over the whole is poured just one pint of water. The pan is placed in the oven and allowed to stand for two hours. Then it is half filled with water and allowed to boil gently, the scum being taken off continually. After two hours more add half a leg of mutton, half a hare or rabbit, two old chickens and two old partridges, all cut up, besides celery and parsley roots, cabbage, turnips and carrots, also cut in slices. Then the pan is filled to the brim with water and allowed to boil for five hours.
The olio is then finished. It is put aside to cool, so that all the fat forming a crust on the top can be taken off. The soup then is poured through a fine wet napkin. Will keep for a few days.