Preheat oven to 325°F (160°C). Score the pork skin deeply in a diamond pattern, being careful not to cut into the meat. Pat the pork knuckle very dry with paper towels. Rub the knuckle all over with salt, pepper, caraway seeds, and minced garlic. Heat vegetable oil in a large, oven-safe roasting pan over medium-high heat. Sear the pork knuckle on all sides until browned, about 5-7 minutes. Remove the knuckle from the pan and add the chopped onion, sautéing until softened. Return the pork knuckle to the roasting pan. Insert metal skewers through the knuckle to help keep the skin taut. Pour the dark beer and chicken or beef broth into the pan around the knuckle. Bring the liquid to a simmer. Cover the roasting pan tightly with foil and transfer to the preheated oven. Roast for 2 hours, basting occasionally. Remove the foil and continue roasting for another 1 to 1.5 hours, basting every 30 minutes, until the internal temperature reaches 160°F (71°C) and the meat is tender. Increase oven temperature to 400°F (200°C). Roast uncovered for 30-45 minutes, or until the skin is incredibly crispy and golden brown. Watch carefully to prevent burning. Remove the pork knuckle from the oven and let it rest on a cutting board for 15-20 minutes before serving. Skim fat from the pan juices and strain to make the gravy, seasoning to taste.