Preheat the oven to 160C (350F), Gas mark 4. Heat a large heavy-based casserole with a lid over a fairly high heat. Add the oil to the casserole and then quickly sear the shanks until nicely browned all over. Add the bouquet garni, carrots, garlic, celery and onion. Pour in the red wine to deglaze the pan, stir in the tomato puree and water. Season with salt and black pepper, then cover with a lid and cook for 2-3 hours until tender. When the shanks are cooked, skim the liquid, drain over a bowl. Reserve this stock to use when cooking the barley and keep the vegetables for the rissoles. Discard the bouquet garni. When the lamb has cooled, finely shred using your fingers.
To make the rissoles, peel and boil the potatoes until tender. Place in a bowl with the shredded lamb, roughly crushing the potatoes. Sauté the onion in half the oil and butter until softened but not coloured. Add to the lamb and potato, then add the parsley, egg and season. Add in the mashed cooked veg from the lamb shanks. Shape into rissoles. Dust in the seasoned flour. Coat in the breadcrumbs. Increase the oven temperature to 200C. Heat the rest of the butter and oil in a large ovenproof frying pan and sauté the rissoles until golden brown. Transfer to the oven and cook for another 10 minutes until completely heated through.
Brown the lamb rack in hot oil. Transfer to a hot oven set at 180C for 10-12 mins. Leave to rest on a cold tray for at least 15 mins.
To make the Scotch broth, cook the barley in the chicken stock over a low heat for 30 minutes. Add the vegetables and pour in the reserved lamb stock. Season to taste, then cover with a lid and cook gently for another 30 minutes or so until the vegetables and barley are completely tender.
Slice the rack into cutlets (2-3 each). Serve with the rissoles and Scotch broth, however you could leave the rissoles out if you’d prefer a simpler meal.