Preheat the oven to 325 degrees F.
Season the lamb with salt and pepper and place in a large casserole. Add the mushrooms, leeks, wine, olive oil and pepper flakes, and toss well to coat and combine. Place the casserole in the oven and cook 90 minutes, stirring every 15 minutes. The meat should be well done and tender and the juices should be bubbling. Serve immediately.