Cullis, or thickened Gravy.—(No. 189.)
To a quart of gravy, put a table-spoonful of thickening (No. 257), or from one to two table-spoonfuls of flour, according to the thickness you wish the gravy to be, into a basin, with a ladleful of the gravy; stir it quick; add the rest by degrees, till it is all well mixed; then pour it back into a stew-pan, and leave it by the side of the fire to simmer for half an hour longer, that the thickening may thoroughly incorporate with the gravy, the stew-pan being only half covered, stirring it every now and then; a sort of scum will gather on the top, which it is best not to take off till you are ready to strain it through a tamis.195-‡
Take care it is neither of too pale nor too dark a colour; if it is not thick enough, let it stew longer, till it is reduced to the desired thickness; or add a bit of glaze, or portable soup to it, see No. 252: if it is too thick, you can easily thin it with a spoonful or two of warm broth, or water. When your sauce is done, stir it in the basin you put it into once or twice, while it is cooling.