Place pan on the heat. Dust the mutton in some seasoned flour and then add the dripping to the pan until it begins to smoke. Fry the mutton in the dripping until it is brown. Cook in the batolies and then deglaze the pan with the stock. Place the lamb in a casserole dish with the peas, sorrel, stock, butter, sugar and the onions. Bring them to the boil and stir in the lettuce and then place it in a medium oven for 2 1/2 hours. Half an hour before the end of the cooking add the mushrooms and the cucumber (stir them in with some water if it is too thick). Blanch the asparagus in the boiling salted water and then keep it all warm. Pour the casserole into a dish and garnish with some asparagus and some picked chervil.