Venison Gravy for Mutton (One wine-glass of sherry one)

A sweet-sharp sherry sauce meant to make roast mutton taste like game. The whole thing takes five minutes once you have gravy or stock to hand.

• Catsup means mushroom or walnutIn an English kitchen of this date, unqualified "catsup" most likely means mushroom ketchup, or walnut: thin, dark, salty and intensely savoury. Tomato ketchup will make the sauce sweet and bright red instead of gamey; use mushroom ketchup, or a teaspoon of Worcestershire sauce plus a little soy if you cannot find it.
• Wine-glass and spoon sizesA Victorian wine-glass is about 2 fl oz (a scant quarter cup). A dessert-spoonful is 2 teaspoons; a tablespoonful of that era is close to the modern one.
• How much stock"As much stock as these ingredients put together" means match the combined volume of sherry, vinegar and ketchup, so roughly 1/3 cup. If you have the pan juices from the mutton, use those first and top up with beef or lamb stock.
• Lumps of sugarLoaf sugar was broken into lumps by hand and sizes varied; if each is taken as roughly a teaspoon, six to eight lumps is something like 2 to 2 2/3 tablespoons. That is sweet by modern taste against only about 2/3 cup of liquid; start with half and add more once the vinegar and stock are in balance.
• Thickening"A little thickening" is unspecified; in a kitchen of this date it would most likely be flour worked into butter, or a spoonful of the flour-and-fat browning kept on hand for gravies. Whisk in small pieces off the boil so it disperses before the sauce tightens.
• The minute mattersThe instruction not to boil more than a minute is the hinge. Longer cooking drives off the sherry's aroma and concentrates the vinegar, leaving a sauce that tastes flatly sour rather than winey.
• Vinegar choiceUse a wine vinegar rather than malt or cider; malt vinegar is too assertive for the small quantity of stock here.
• YieldMakes roughly 3/4 cup, enough to sauce mutton for four to six as an accompaniment rather than a pouring gravy.