Among the foods known longest to man - dried grains have been found in Peruvian and Aztec tombs, as well as among the remains of the lake dwellers in what is now Switzerland - they are also among the most versatile. Use beans - white haricot, red kidney, lentils, peas and flageolets - to give variety, richness and excitement to your winter meals. Feature them in warming country soups, or smooth purées to accompany meat, poultry or game. Make them, with pork, lamb, duck, goose or game, the highlight of an informal luncheon or supper. Serve a refreshing salad of cooked beans flavoured with onion, parsley, olive oil and wine vinegar.