Polpettone with Onions

This is Diana’s recipe. She is a wonderful and elegant nonna and cook. She asks for the mince to be passed twice through the mincer as she likes it fine for this. Even though there are eggs it’s quite delicate and you have to take care while turning it in the pan so it doesn’t break. If possible, use a large non-stick frying pan with fairly high sides so that you can put a lid over the hill of meat in the pan. Lovely with a dish of sliced tomatoes on the side.