Place 1 litre (1¾ pt or 4½ U.S. cups) of well-reduced purée of fresh tomatoes in a pan and reduce whilst adding approximately 7 dl (1¼ pt or 3 U.S. cups) of ordinary aspic jelly, a little at a time. Reduce until the total quantity is approximately 1 litre (1¾ pt or 4½ U.S. cups). Pass through a fine strainer and stir until the Chaud-froid reaches the correct stage for coating.