Finely chop the onion, carrot, celery and garlic.
Heat the oil in a pan then gently sauté the chopped vegetables for about 8-10 minutes until they've softened.
Add the tomato purée and marjoram, then stir for a minute.
Chop the tomatoes and add to the vegetables. Stir for a minute.
Add the stock and bring to the boil.
Cook for 15 minutes, then add half of the peas and cook for 5 more minutes.
Add the parsley and half of the mint. Using a hand-held blender, blend the stew until you get a thick, lightly textured sauce. Taste and adjust the seasoning to your liking.
Meanwhile, cook the meatballs according to the packet instructions - you can fry, grill or bake them. It should take about 15-20 minutes.
Add the remaining peas and the meatballs to the sauce and bring back to the boil. Cook for 3-5 minutes, then serve, garnished with mint leaves.