Lamb shoulders are very fatty so remove as much as the fat from the meat as possible.
In an oven proof pan gently brown off the pancetta in a tiny amount of olive oil; just enough to get it going and not stick.
Use a slotted spoon to remove the pancetta and keep it handy on the lid. Then turn up the heat and brown the lamb in the pancetta fat making it nice and brown on all sides. Reserve the lamb with the pancetta.
Brown the onions then add the carrots and celery, giving them a few minutes to soften before adding the bay leaves, rosemary and garlic.
Add some of the stock and with a wooden spoon scrape any bits catching on the base of the pan before adding the rest. Add the lamb and pancetta. Season to taste.
Cook in the oven at 180 degrees C for 2 hours and serve with greens and mashed potato.