Preheat the oven to 375 degrees F.
In a large bowl add the lamb shanks and flavoring ingredients (from the top until the olive oil only) and toss well. Spread the lamb in an oven safe baking dish.
Add in the whole spices, cut up onions and garlic. Try to squeeze them in the dish and divide them evenly so the flavor spreads evenly as well.
Pour the stock over the lamb dish and cover the plate with foil. Roast the shanks until tender--this should take between 100-120 minutes (depending on the size of your lamb shanks).
Once ready, remove the foil and if the lamb requires more browning, leave it in the oven for an extra 10 minutes. Note: USDA recommends cooking lamb to a minimum 145 degree internal temperature with a 3 minute rest.
In the meantime, make the skyr sauce.
Mix the skyr, garlic paste, fresh dill, lemon juice, salt and pepper, and chili flakes together in a bowl until blended.
On a serving plate, spread the skyr.
Add the lamb shanks on top and garnish with your choice of garnishes.