Meatballs with mantilla is a typical preparation of the Garrotxa, Osona and Ripollès regions, which you may find ready made in some butchers. They are usually eaten on their own, freshly made or stewed with a little chopped fried onion, pepper and tomato, bound with a roux. The caul or mantilla (in Catalan, "farmer’ wife’s apron") is the lacy membrane covering a pig’s liver. It is used to make these meatballs, or for "liver bread", a type of pâté made with pig’s liver, bacon, pork cheeks and eggs which is prepared in the area from La Cerdanya to Empordà, including Vallespir.
Mince the lean pork, veal and bacon. Soak the caul in warm water and the juice of half a lemon to eliminate its strong smell and make it stretch better. Place in a basin and knead together with the finely chopped garlic, the eggs, the bread crumbs, well squeezed, and salt and pepper. When it is all well mixed together, form into balls a little larger than normal meatballs, wrap them in pieces of caul, and press to flatten slightly. Trim the ends. Dip in flour and fry in a frying pan with hot oil on one side, then turn them over and fry the other side. They should be golden on the outside and done inside. Drain on absorbent paper to remove any excess fat and serve immediately. They can also be left to cool and eaten for tea on bread spread with tomato, or stewed in a well-concentrated sauce of finely-chopped onion, garlic and tomato, with a picada added just before the end.