Hand shred Lion's Mane Mushroom into small pieces resembling texture of flakey crab.
In a large bowl add: 1 slightly beaten egg, ¼ cup finely diced onion, 1 tablespoon mayonnaise, 1 teaspoon Worcestershire sauce, ¾ teaspoon old bay seasoning, 1 teaspoon Dijon mustard, 1 tablespoon finely chopped parsley, ¼ teaspoon salt, and ¼ teaspoon pepper. Mixing well.
Thoroughly mix in shredded mushrooms and ½ cup breadcrumbs.
Form mixture into 3 to 4 equal size round flat patties about ½ to ¾ inch thick.
Heat 2 to 3 tablespoons oil in a sauté pan on medium to high heat.
Cook patties for approximately 2 to 3 minutes per side until golden brown and cooked throughout.