Bring 3 cups of water to a boil and add minced onions. Immediately remove water from heat and pour into a strainer. Drain parboiled onions well, pat dry and set in a bowl. Soak bread crumbs in milk for 10 to 15 minutes. Drain through a sieve and press down lightly to squeeze out excess milk (but leave moist). To the onions add the ground beef and mix together with a fork. Add the parsley and mint, salt and pepper. (To taste for seasoning, first heat some of the mixture in a skillet; taste, then adjust seasoning). Set aside, refrigerated and covered for 1 hour to firm up. When ready to cook your meatballs, take a teaspoon of the meat mixture and form a ball the size of a walnut. To help shape the mixture dip your hands in cold water. Shape meatballs smoothly but don't overwork the meat. When all meatballs are shaped, heat oil and butter in a large skillet. Lightly dredge meatballs in flour and shake off excess. Saute meatballs for about 4 to 5 mins a side or until just done. They should be just cooked through, but still moist inside. Pat dry on paper towels. When ready to serve, place meatballs in the tomato sauce (see recipe below) to reheat and serve atop spaghetti.