Prepare the Mushrooms

1. Marinate: In a bowl, combine sliced mushrooms, broth, garlic powder, steak seasoning, and smoked paprika. Let sit for at least an hour, or overnight for deeper flavor. Stir once or twice to coat evenly.
2. Drain: Place a fine-mesh strainer over a bowl and press to remove as much liquid as possible. Break up any clumps and press again until the mushrooms are nearly dry.
3. Bake: Preheat oven to 300°F. Lightly oil a baking sheet and spread the mushrooms in an even layer. Bake for 15–20 minutes, stir, then bake another 10–15 minutes, until reduced, slightly dry, and concentrated—but not crispy.
4. Rest: Transfer mushrooms to paper towels and let sit briefly to absorb excess moisture.

Make the Sauce

1. In a small bowl, whisk together vegan mayo, chopped dill pickles, sriracha, and Worcestershire sauce. Set aside.

Assemble the Sandwiches

1. Toast the Bread: Heat a cast-iron pan or skillet over medium heat. Lightly butter or oil the rye bread and toast until golden. Add the cheese and cover briefly so it melts.
2. Layer It Up: Layer mushrooms, sauerkraut, and a generous amount of sauce. Add red cabbage if using.
3. Serve Immediately: Cut in half, grab some napkins, and dig in!