Go over the joint and remove any large fat deposits or unsightly skin.
Stab the joint several times over with the tip of a small sharp knife and insert one ½ clove of garlic per incision. Also stick in a little sprig of rosemary per incision to enhance the flavour.
Place the shoulder on the lamb bones with the 2 carrots cut just in half, drizzle over the olive oil and season with sea salt and pepper.
Place in the oven at 160°C for 4-5 hours, covering with a sheet of foil for the first 3 hours. With one hour to go, throw in the peeled shallots and remove the foil.
When the lamb is cooked and the shallots are also cooked, remove everything from the tray and allow to rest somewhere warm.
Add the tomato puree and flour to the cooking tray and place back on the stove to cook slightly. Then add the stock and bring to the boil.
Strain through a very fine sieve into a clean pan and bring back to the boil. Season if required.
Carve the lamb onto a warm serving dish, place the shallots around and put the gravy into a sauce boat.
Serve with green vegetables and some potatoes.