Place the carrot, onion, leek, celery, and pork knuckles into a large stockpot. Throw in the peppercorns, and season with salt to taste. Add enough water to the pot to cover the vegetables. Cover, and cook over medium heat for 2 to 3 hours, or until everything is tender. Remove the knuckles from the water, and drain. Reserve vegetables and cooking liquid.
Preheat the oven to 425 degrees F ( 220 degrees C). Melt the shortening in an enamel coated cast iron baking dish or pan. Place the drained pork knuckles, cooked vegetables, and about 2 cups of the cooking liquid into the pan.
Bake for 30 minutes in the preheated oven. During the last 10 minutes, sprinkle with beer in which a good amount of salt has been dissolved. Dust lightly with cumin to increase flavor. Serve with potato or white bread dumplings, or sauerkraut salad. In Bavaria, the cooking liquid and juices are strained, and served as an accompanying sauce.