Soak the Römertopf for at least 30 minutes before use.
Wash and dry pork knuckles and season with salt and pepper to taste. Cut the rinds crosswise. Peel and quarter the onions. Place the knuckles and onions in the Römertopf, put the lid on and put in the cold oven.
Cook at 175 ° C for between 2 1/2 and 3 hours, depending on the size.
Occasionally check whether too much fat has not been left out, if necessary reduce the amount of fat. Then bake the knuckles without a lid for about 30-45 minutes until crispy.
Take the knuckles out of the pot and keep warm. Mix the onions and fat using a hand blender. Thicken with flour (or sauce thickener) and season to taste.
As a side dish, of course, dumplings and red cabbage go well. Bavarian cabbage or Bavarian cream cabbage are equally good alternatives. A simple dark Bavarian beer is recommended as a drink. More than two knuckles are difficult to prepare in the Römertopf due to lack of space.
The knuckles are - like everything in the Römertopf - wonderfully tender. In order not to adversely affect the taste of the knuckles, I refrain from pre-cooking the knuckles in a (pressure) saucepan. The fine taste of the Römertopfhax`n should not be overwhelmed by a heavy sauce. That`s why I prepare the sauce as sparingly as possible.