Wash the potatoes thoroughly, cover and cook in plenty of boiling water for about 20 minutes. Peel onions and cut them into fine slices. Clean, wash and drain lettuce well. Cut lettuce into strips. Heat the fat in a pot and fry the onions in it. Add cream, stock and a little salt and bring to the boil. Add deep-frozen peas and cook covered for about 6 minutes.
In the meantime, drain the potatoes, rinse with cold water and peel the skin. Keep potatoes warm. Wash chervil, shake dry and chop except for something to garnish and sprinkle. Stir the chervil into the peas and season with pepper. Fold in lettuce and immediately arrange on plates with the potatoes and cottage ham. Garnish with chervil and sprinkle