Stone the apricots and stew them till soft in the water. When soft rub them through a hair or nylon sieve. Meanwhile crack the stones, scald and skin the kernels: Add sugar, lemon juice, liqueur (if used) and kernels to the sauce. Reheat the sauce, stirring in the arrowroot blended with a little cold water. Bring to the boil and serve the sauce.
See also Jam Sauce.