Heat the grill to medium hot. Clean the mushrooms with a damp piece of kitchen roll, and then brush lightly with the vegetable oil.
Place the mushrooms under the grill, cook for 5 minutes, turning once. Keep warm.
While your mushrooms are cooking, mix together the turkey mince, oregano, sumac, salt and pepper. Shape into 8 thin patties, about 7cm diameter. Cook under the grill for 8-10 minutes, turning once. Check that the juices run clear when cooked.
To assemble, place the a cooked mushroom on each place, top with a few baby spinach leaves. Add on the first burger, top with 2 slices of cucumber, then the second burger and finally the slice of beetroot. Secure with a wooden skewer.