Preheat the oven to 190ºc / 375ºf / gas mark 5 and season the lamb racks all over with salt and pepper
In a small pan, melt the butter and marmalade with a little salt and pepper, then stir in the mustard. Remove from the heat and add the breadcrumbs. Stir well and spoon evenly across the racks, pressing the crumbs down firmly with your hands over the meat
In a separate pan, sauté the onion and garlic in olive oil, then add the rosemary
Wash the baby vegetables, place them in a roasting dish and mix in the sautéed onions and garlic. Season well, then top with the crumbed lamb racks.
Roast in the centre of the oven for 20 to 30 minutes depending on how you like your lamb cooked. Remove and rest for 10 minutes before serving
Take the racks and carefully cut in half - try not to disturb too much of the crust. Drizzle the balsamic vinegar over the vegetables, then spoon them onto warm plates and top with the lamb before serving