Choose a new cookbook worth up to £28 when you subscribe to our magazine.
Put the celeriac, swede and potato in a large steamer, then steam for 25 mins until softened.
Meanwhile, heat the oil in a large non-stick frying pan and fry the onions for 10 mins until softened and golden. Push to the side of the pan, then add the lamb and rosemary and stir-fry over the heat until browned, but still a little pink in the middle – try not to overcook it as it will become tough and will need a longer cook to become tender again. Add the bouillon and balsamic vinegar with 200ml boiling water. Stir to make a sauce.
Mash the steamed veg and spoon half into the centre of two plates. Top with half the lamb and gravy, scatter with the parsley and serve with the spinach and peas. Chill the remaining lamb and veg to reheat and serve on another evening.