Gooseberry Sauce

A sharp fruit sauce of the plainest kind, meant for oily fish. The whole point is the acidity of unripe fruit, so resist the urge to sweeten it into a compote.

• Green gooseberriesThese are hard, sour, underripe fruit picked in late spring or early summer, not the soft dessert berries sold ripe. Frozen gooseberries work; ripe ones will give a sauce that is sweet rather than cutting.
• A pint of fruitMeasured by volume. Depending on whether an imperial or a smaller pint is meant, that is somewhere between about 12 oz (340 g) and a pound of berries; the recipe gives no yield or number of servings.
• Ten grains of gingerA grain is an apothecary weight of about 65 mg, so ten grains is around two-thirds of a gram, close to a quarter teaspoon of ground ginger. The original may equally mean ten small pieces of bruised root; the quarter-teaspoon reading is the safer starting point, and it should register faintly rather than dominate.
• Lumps of sugarLoaf sugar was nipped into lumps of no fixed size; a couple of teaspoons' worth is a reasonable starting point. Add and taste, since the tartness of the fruit is the reason for the sauce.
• StrainingPush the cooked fruit through the colander with a wooden spoon or ladle to leave skins and seeds behind. A food mill does this faster and more thoroughly than a sieve.
• Cooking waterCover the berries barely -- excess water gives a thin sauce. If the strained purée is loose, reduce it a little before the sugar and butter go in.
• Boil upA brief return to the boil to melt the butter and dissolve the sugar is all that is wanted. Prolonged boiling after the butter is added will split the sauce.
• ServingSend it out warm with grilled or fried mackerel, herring or oily white fish, and with roast goose or pork if there is any left over.