I have slow cooked mutton shoulder a few times - it has such good flavour and my source is really good and comparitively cheap. I brown the shoulder the throw in 3 or 4 squashed (but still whole) garlic cloves, some sprigs of thyme and some of rosemary, a bit of stock (or in my case a stock cube) and half a bottle of white wine. Cover with a buttered paper lid and bake. The recipe I have modifed says 160C or 140C in a fan oven for something like 3 hours. I do it at 140C for anything from 3-4 hours, just check every now and again to make sure there is still liquid in the pan. Pour off the worst of the fat and turn the remaining liquor into the gravy. Yum, I have some cold in the fridge left over from the weekend which I plan on eating tonight! For anyone in the UK it is a heavily modified version of the Anchor and Hope recipe in this months (maybe last months) olive magazine. Oh, thing shoulders that I have used have been more like half shoulders and have weighed about 1.5kg.
I haven't but we did slow roast an expensive shoulder last night. It was very fine with a deep lamby flavor and excellent jus. It roasted at a very low temperature for about four hours. Used a recipe in the the River Cottage Meat cookbook (another British chef/author).
We started with fresh goat cheese crostini and ate the lamb with artichokes braised in the pan and herbed spaeztle.
I can post the recipe if you like. Highly rec all of his books for a simple, purist approach to excellent meat.
Adapted from River Cottage Meat (Metric)
1 large shoulder of mutton, hogget, or mature lamb (weighing about 3-4 kg)
2 T olive oil
1 kg onions
1 kg potatoes
6 large garlic cloves
1 large glass of white wine
About 500 ml water or lamb stock
(We salted our lamb and let it rest overnightt + skipped the potatoes although they sound lovely in the recipe)
Massage oil into the lamb and roast for thirty minutes at 220C.
Remove lamb and pour off fat if excessive. Deglaze pan with wine. Scatter the garlic cloves and rest the lamb on the thinly sliced onions. and potatoes. Pour over stock (used homemade chicken) it should not quite cover the potatoes. Return to over and cook 4 hours at 140C. Remove the lamb to rest, stir the onions and potatoes, crisp potatoes at 220C.
Serve the meat, which should be tender enough to scoop with a spoon, with spoonfuls of the crispy-topped creamy-underneath onion potatoes. (Our meat was very tender although not spoonable. It would have needed another hour or so. However, it was really lovely and did not need more cooking.) It could have easily taken other spices or braising elements but didn't need them.