In a Dutch over set over high heat, melt a good amount of cooking fat, preferably lard.
While the Dutch oven is heating up, mix the spices together in a large plate. Pat the pork shanks dry and dredge them in that spice mixture, making sure that all sides are well covered.
Add the shanks to the hot Dutch oven and sear them nice and good on all sides, until a nice dark brown crust forms, about 3-4 minutes per side.
Add the onion and parsley, plus the water mixed with savory, mustard, coriander as well as the rest of the spice mixture that didn't get used to coat the pork shanks earlier.
Bring that to a boil then cover and transfer to the oven for about 3 to 3½ hours, until the meat is super tender and falls off the bones.
Remove the shanks from the cooking liquid and allow them to cool for a while, until you can safely handle them. Pick the meat out and set it aside; discard bones and fat.
Strain the cooking liquid (you can skim some of the surface fat with a spoon first if you want to) through a fine mesh sieve set directly over a medium saucepan. Bring to a boil over medium-high heat.
Mix the tapioca starch with the 2 tablespoons of water and pour that right into the cooking liquid. Continue cooking for about one minute, or until the sauce is thickened. Return the meat to the saucepan, stir well and cook over medium-low heat until heated through, and then serve.