Blanch the lettuce leaves for 2 minutes in boiling water and drain.
Soak breadcrumbs in milk for 10 minutes then squeeze out excess milk.
Soften butter, stew onion, garlic, celery, carrot, and parsley.
Add chopped meats and stir until pale golden then add flour and stock.
Cook for 15 minutes until the stock is absorbed.
Blend in a food processor until smooth.
Add soaked breadcrumbs, egg-yolk, Parmesan, marjoram, salt, pepper, and nutmeg. Blend until smooth.
Place a mound of mixture on each lettuce leaf, roll up, and tie with string.
Poach bundles in simmering broth for 10 minutes before serving.
Lift out with a perforated spoon, untie the string, and serve in soup plates.