Fry the bacon in oil until crisp. Add the remainder of the meatball ingredients to a bowl and plenty of cracked black pepper. Mix well.
Shape the mixture into meatballs just larger than a walnut. Using the same pan as for the bacon, fry the meatballs until browned on all sides – you may need to do this in two batches – then cover and set aside.
Preheat the oven to 190 degrees Celsius. Put all of the sauce ingredients in a saucepan and bring to a boil. Reduce the heat and simmer for a few minutes until the sauce has thickened slightly.
Cover the base of a casserole or gratin dish with the meatballs, aligned evenly, leaving space in between each one. Pour the sauce obto meatballs, ensuring that it fills all the gaps.
Sprinkle the cheese, then place in the oven for 20 to 25 minutes, or until the cheese on top is browned. Serve with a large green salad.