Shred King Oyster mushroom stems with a fork and finely chop Cremini mushrooms. Place in a large bowl.

In a small bowl, whisk together 2 tbsp oil, soy sauce, miso paste, paprika, garlic powder, onion powder, and pepper.

Pour the marinade over the mushrooms and massage it in. Sprinkle flour over the mixture and toss until a sticky mixture forms.

Divide the mixture into 4 equal portions and pack tightly into balls. If too loose, add a little more flour.

Whisk mayo, sriracha, 1 tsp soy sauce, and sesame oil to make the umami sauce. Toast the buns.

Heat a cast iron skillet over medium-high heat until smoking. Add a little oil. Place mushroom balls in the pan, cover with a square of parchment paper, and smash flat with a heavy press.

Cook undisturbed for 2-3 minutes until edges are crispy and deeply browned. Scrape underneath, flip, and immediately top with cheese.

Cook 1-2 more minutes until cheese melts. Assemble burgers with toasted buns and umami mayo.