Place a large frypan over medium heat on the stovetop. In a shallow dish or bowl mixt together sumac, salt and plain flour. Dust the venison shanks in the flour and set aside.
Add a splash of evoo to the frypan and fry the shanks on all sides until golden brown.
Pour approx 30gm of evoo into a small saucepan and add fennel seeds, coriander seeds and salt and set aside.
Once the shanks have sealed transfer them to a large dutch oven or skillet with a lid. Add the potatoes and stock to the shanks and place a lid on top. Place the shanks into a pre-heated oven combi setting 150 °C for 2 hours.
Place the small saucepan of oil fennel and coriander seeds over medium heat for 2-3 minutes until fragrant.
Pick parsley, dill and coriander leaves into a small mixing bowl. Peel the skins from the tomatoes and finely dice. Add the diced tomato to the herbs and set aside.
Once the fennel oil has cooled slightly pour it into the bowl of herbs, mix well and set aside.
Once the venison has cooked remove it from the oven and remove the potatoes. Return the venison to the oven for a further 30 minutes.
Mash the potatoes through the ricer and mix through approx 30gm of evoo and salt. Cover with cling film and set aside.
Once the venison has finished cooking remove it from the oven and change the setting to steam setting 100 °C. Place the skordalia (mash) in the oven to warm through for 5-6 minutes.
Pick the flesh from the shanks and discard the bones. Once the mash is warm spoon it onto a large serving platter. Top with the picked venison shank and some of the cooking liquid. Finish the dish by scattering over the sauce vierge (herb, tomato and oil mixture) and serve.