Coat the bottom of a large skillet with oil and place over medium heat. One oil is hot, add mushrooms in an even layer. Allow to cook for about 5 minutes, flip and cook 5 minutes more, until nicely browned on both sides. Add onion and cook 5 minutes more, flipping occasionally, until onion is soft and translucent. Add garlic and cook 1 minute more, until very fragrant. Remove from heat and allow to cool for a few minutes.

Transfer mushroom mixture to a food processor bowl and add chickpeas, panko, soy sauce, Worcestershire sauce, vinegar, liquid smoke, cumin and pepper. Pulse until ingredients are finely chopped and well blended. Shape the mixture into 4 to 6 patties.

Place the same skillet that you cooked the mushrooms in over medium heat, adding a dash more oil if needed. Working in batches if needed, place patties into skillet and cook about 4 minutes on each side, until browned.

Place cashews, ¾ cup water, onion, ketchup, vinegar, hot sauce and Worcestershire sauce into blender or food processor and blend until smooth. Thin with up to an additional ¼ cup of water, if needed. Add pickle relish and pulse just until mixed in. Season with salt and pepper to taste.

Stuff buns with patties and top with vegan Russian dressing, sauerkraut, lettuce and tomato. Serve.