Put the minced beef and pork in a large bowl together with the breadcrumbs, eggs, chopped parsley, salt, pepper and sugar.
Fry the onion gently in the butter until soft. Add to the other ingredients in the bowl and mix well, adding a little lager if the mixture is too dry (if, for example, you overdid it with the breadcrumbs). Roll into walnut-sized balls.
Fry the meatballs for