BROWN ONION SAUCE

Cut off both ends of the onions, and slice them into a saucepan in which two ounces of butter have been dissolved; keep them stewing gently over a clear fire until they are lightly coloured; then pour to them half a pint of brown gravy, and when they have boiled until they are perfectly tender, work the sauce altogether through a strainer, season it with a little cayenne, and serve it very hot.