Heat oil in pan over med-high heat and sauté onion for about 8 minutes, or until onion is translucent and has softened. Add garlic, paprika, thyme, and cumin. Cook for a few more minutes until spices are fragrant.

Add mushrooms and continue to cook until moisture from mushrooms has evaporated, about 10 to 15 minutes. Stir in ground seitan and cook for another 5 minutes. Add uncooked rice, diluted tomato paste and parsley. Stir to combine then remove from heat.

Cut end off head of cabbage. Carefully remove leaves and rinse. Choose 20 or so of the best leaves. Place clean towel on the counter. Put a single leaf on the towel and with a rolling pin, firmly roll over the spine of the cabbage to crush. This will make it easier to fill and roll. Repeat with remaining leaves.

Preheat oven to 350° F. Place half of the sauerkraut in the bottom of a 9-inch by 13-inch casserole dish. On a cutting board or mat, lay out one cabbage leaf. Place about 1/4 cup of filling and roll, while tucking in ends. Place seam side down on top of cabbage in casserole dish. Repeat with remaining leaves. Scatter remaining sauerkraut on top of rolled cabbage. Pour tomato juice over cabbage leaves so it comes about halfway up the sides of the dish. If you have leftover leaves, you can place them on top of rolled cabbage.

Cover pan tightly with foil, and place it on a baking tray. Bake for about 1 1/2 hours. Remove from oven and let rest 15 minutes before serving. Dish can be made a day in advance and reheated at 300ºF for about 30 to 40 minutes or until a sharp knife inserted into a roll feels hot. Remove pan from oven and let sit for about 5 minutes, then serve.