Jane Grigson describes how to cook and prepare ox tongue in some detail in English Food as well as providing several recipes. Most use pickled ox tongue, but for some it is not specified and I had a calf tongue to use. Many recipes require a cooked, boiled tongue (including the next recipe), but there is no guidance on the preparation of calf tongue. I did a bit of reading and came up with my own method which I am now imparting upon you good people, natch.
The tongue before cooking
Start by soaking the tongue for six hours, changing the water a couple of times. Place it in a closely-filling pan with some cold water to just cover along with an onion studded with two cloves, a chopped carrot, a stick of celery, a bay leaf, a sprig of time, a bay leaf, some crushed peppercorns and a teaspoon of salt. Bring slowly to boil, skimming away any grey foam that may rise. Turn the heat as low as possible, cover, and simmer gently for an hour (I erred on the side caution and cooked it for best part of an hour and a half, but it was definitely over-cooked). Remove the tongue and as soon as it is cool enough to handle, peel the skin away and cut away any gristly bits and blood vessels. The tongue can then be used as required in your recipe.