Put the butter into a stewpan, set it on the fire, and, when browning, throw in the onions, which must be cut into small slices. Fry them brown, but do not burn them; add the flour, shake the onions in it, and give the whole another fry. Put in the gravy and seasoning, and boil it gently for 10 minutes; skim off the fat, add the mustard, vinegar, and lemon-juice; give it one boil, and pour round the steaks, or whatever dish the sauce has been prepared for.
Time: Altogether 1/2 hour.
Seasonable at any time.
Sufficient for about 2 lbs. of steak.
Note: This sauce will be found an excellent accompaniment to roast goose, pork, mutton cutlets, and various other dishes.