1. To prepare the brine, fill a large container with 2 gallons of cold water; stir in salt, sugar, and pickling salt.
2. Add pork hocks to brine; cover and refrigerate for 72 hours, stirring once a day.
3. Preheat oven to 375ºF.
4. Remove pork hocks from brine and rinse with cold water. Transfer pork hocks to a large roasting pan and sprinkle with pepper and caraway seeds.
5. Add onions and celery stalk to the roasting pan and season pork hock with Maggi sauce.
6. Add 4 cups of water to the roasting pan. Roast pork hocks for 2 ½ hours, or until meat pulls away easily from the bone.
7. Remove pork hocks from roasting pan and transfer the drippings to a small pot; thicken gravy with flour and cornstarch and stir over medium heat until thickened for 2-3 minutes, or until gravy is thick enough to coat the back of a spoon.
8. Slice pork hocks into ¾-inch slices and plate. Spoon gravy over the pork hocks. Pork hocks are best served with sauerkraut and roasted vegetables.