The cooking technique of braising involves cooking meat and vegetables slowly in a flavorful liquid in a covered casserole dish in the oven. It is particularly useful for bringing juicy tenderness to tough, lean meats such as game like venison, and to fibrous vegetables such as celery, leeks, onions and other ingredients. You do not need to add oil or butter to the braising sauce; the flavor should come from ingredients such as good stock, wine and fresh herbs.