Heat the oil in a large frying pan and cook the lamb steaks in batches for 2 mins each side until browned. Remove the lamb from the pan and set aside.
Add the onion and garlic to the pan and cook for 3-4 mins until beginning to soften.
Pour over the chopped tomatoes and add the purée, balsamic vinegar and stock. Stir and bring to a gentle simmer. Return the lamb to the pan and cook over a very gentle heat, covered, for 20 mins.
Stir in the courgette and beans and cook for a further 15 mins, uncovered, until the lamb is tender and you have a thick sauce.
Snip the lamb into bite-size pieces with scissors and return to the sauce
Cook's tip: to serve toddlers, stir the sauce through the pasta.