If you have part of a cold chicken, its liver, perhaps some calf’s liver, and may be some pork, then you can make an excellent large terrine with what you have in hand. Otherwise buy or reserve what you will need and make say 2 or 3 terrines and 2 or 3 smooth pâtés at the same time for use over the next weeks or months.
Remember to season highly: more than you would for most dishes. All cold food has less flavour than hot, and the dense packed consistency of terrines and potted meats seems to absorb flavours. You will want onions and herbs for some recipes, garlic or garlic salt, mace, nutmeg, turmeric, powdered ginger and thyme; and black and white pepper and salt for almost all. You will need some wine or brandy and probably a good well-seasoned stock made from the meat or bird you are using (see below). Mace and turmeric both bring out the flavour of meat. Mace is particularly good with shellfish. Ginger was often used as an alternative to pepper up to the nineteenth century, but I find that it is particularly good in potted meats as, without being noticeable, it gives them a certain zest. Thyme is very good with beef and all the liver pâtés. The spices of course help to preserve the meat.