“Boil softly in half a pint of well-flavoured pale veal gravy a few very thin strips of fresh lemon-rind, for just sufficient time to give flavour to it; stir in a thickening of arrow-root, or of flour and butter, add salt if needed, and mix with the gravy a quarter of a pint of boiling cream....
Good pale veal gravy, ½ pint; third of 1 lemon-rind; 15 to 20 minutes. Freshly pounded mace, third of a saltspoonful; butter, 1 to 2 oz.; flour, 1 teaspoonful; (or arrow-root in equal quantity; cream, ¼ pint.” (Acton 110)
Mrs. Acton forgot to include the mace in her narrative; add between ¼ and ½ teaspoonful with the peel. Also in terms of modern measurement, use a Tablespoon of flour for each one of butter, one of each for a thinner table sauce, two for use in binding other ingredients. Please note that Mrs. Acton wrote before the advent of imperial measures and therefore used 16 oz pints.
Eliza Acton, Modern Cookery for Private Families (London 1855; Southover Press facsimile edition 1994)