Peel and finely chop the onion and fry in fat until translucent. Fry the meat in portions. Add the herbs, salt and pepper. Put the lid on and cook on a low heat. After a short time, add a little beer. Continue steaming for about 2 hours, adding a little beer in between. For the last half hour, place the mustard-coated bread (mustard facing down) in the saucepan to thicken the sauce.