Piedmont and the Po valley — polpette di bollito are the Monday preparation throughout the bollito misto tradition (which covers Piedmont, Lombardia, and Emilia). The polpette are not a second-rate preparation but the carefully considered sequel to the Sunday feast.
Polpette di bollito (or friciula in Piemontese dialect) are the Monday preparation that follows Sunday's bollito misto — the leftover boiled meats (beef, tongue, cotechino, chicken, or whatever remained from the bollito) are finely chopped or ground, mixed with egg, Parmigiano, breadcrumbs, garlic, and parsley, formed into patties and pan-fried in butter until golden on both sides. This is the most honest expression of the Italian cucina di recupero (recovery cooking) — nothing from the Sunday feast is wasted. The polpette have a softer, more yielding texture than regular meatballs because the boiled meat is already cooked; their flavour is deeply savoury from the broth the meat was cooked in.
Polpette di bollito in the pan, golden from the butter, have a texture unlike regular meatballs — softer, more yielding, with the distinctive flavour of long-boiled meat concentrated into each bite. With salsa verde alongside — its capers, anchovy, and parsley acid-sharp against the mellow polpette — the combination is one of the best Monday lunches in Italian cooking.
Finely chop or grind leftover bollito misto (a combination of different meats produces the best result). Mix with: beaten egg (1 per 300g meat), grated Parmigiano, fine breadcrumbs (just enough to bind), minced garlic, chopped flat-leaf parsley, salt, and black pepper. The mixture should hold its shape when pressed — add breadcrumbs to adjust if too wet. Form into patties of 7-8cm diameter, 1.5cm thick. Dust lightly with flour. Fry in butter over medium heat — 3-4 minutes per side until golden. Serve with salsa verde (the traditional Piedmontese accompaniment) or a simple mustard.
The best polpette di bollito use a mixture of boiled beef and cotechino or zampone — the pork fat from the cotechino gives richness and moisture. Salsa verde piemontese (chopped capers, anchovies, garlic, parsley, and olive oil, with sometimes a hard-boiled egg and a slice of bread soaked in vinegar) is the canonical accompaniment — it provides acidity and sharpness that the mild polpette needs.
Over-working the mixture — the boiled meat is already cooked; it needs only to be bound, not massaged to develop gluten. Too many breadcrumbs — excess breadcrumbs produce a dry patty; just enough to bind is the standard. Frying at too high heat — the patties are already cooked; they need only to be coloured; high heat produces a dark exterior before the interior is warm.
Anna Gosetti della Salda, Le Ricette Regionali Italiane; Slow Food Editore, Piemonte in Cucina