Heat the beef stock slowly. Bring a large saucepan of salted water to the boil. Prepare the lettuce, selecting the middle, fairly large leaves: you will need 12 oz (350 g) of these. Reserve the outermost, old leaves and the very small ones for use in other dishes.

Spread out 3 clean dry cloths side by side on a working surface. Blanch the lettuce leaves one by one for 30 seconds in the saucepan of boiling salted water, remove each one with a slotted ladle and spread out flat on the cloths with the greener, inner side uppermost, taking care not to tear them. Wash, dry and chop the mushrooms.

Fry the veal escalopes lightly in a little butter with a peeled whole clove of garlic; sprinkle with a little salt and pepper when cooked, chop into fairly small pieces and set aside.

Cut both types of ham into strips, then chop finely. Process the veal, ham and the marjoram leaves briefly in the food processor, just enough to chop further and mix well without turning the mixture into a paste.

Transfer this stuffing to a large mixing bowl, stir in the egg yolk, the grated cheese, a little salt and plenty of pepper. Stir until the mixture is evenly blended and homogenous.

Place 1 - 2 tsp of this stuffing in the centre of each lettuce leaf, fold the rib end of the leaf over the filling, fold over the two sides and then roll up, forming a neat parcel; press the edge of the leaf gently to seal.

When all the leaves and stuffing have been used up, arrange the parcels in a single layer, with the joins downwards, in a shallow fireproof casserole dish; sprinkle with about 8 fl oz (225 ml) of the boiling hot stock, cover and simmer gently for 5 minutes. Fry the bread croutons in butter until golden brown and very crisp.

Carefully arrange an equal number of the lettuce parcels side by side in 4 wide, heated, soup dishes; sprinkle some croutons on top of each serving, ladle in the remaining hot broth and serve at once.