Step 1

Shred mushrooms: Cut the tops off the mushrooms, slice as thinly as possible. Set aside. Rake a fork down the base of the mushroom stems to shred them.

Step 2

Make Cabbage Slaw: In a medium bowl, combine cabbage, green apple, scallions, mayonnaise, apple cider vinegar, and grainy mustard. Stir well, until evenly coated. Season with salt and pepper, to taste. Cover and refrigerate.

Step 3

Cook mushrooms: Heat grapeseed oil in a large cast iron skillet over medium-high heat. Scatter mushrooms into hot oil. Use a heatproof spatula to press the mushrooms down into a single layer, maximizing the surface area in contact with the hot pan. Let cook undisturbed until brown on the bottom, 8 to 10 minutes. Flip and cook until golden brown on the other side, about 5 minutes.

Step 4

Season mushrooms: Reduce heat to medium. Add tamari, toss to coat. Cook, stirring frequently, for another 5 minutes. Sprinkle in paprika and garlic powder. Cook until the mushrooms are crispy on the edges, about 5 minutes. Pour in barbecue sauce, stir to coat. Cook until sauce is sticky and hot, about 3 minutes.

Step 5

Assemble: Open the toasted buns, spread with mayonnaise, top with mushrooms and cabbage slaw.