Make your flax egg, set to the side (about 5-10 minutes until it starts to thicken).
Hand shred Lions Mane Mushrooms into small pieces that look similar to a flakey crab consistency.
In large bowl, combine flax egg, mayo, onion, Worcestershire sauce, Old Bay Seasoning, Dijon Mustard, Parsley, salt and pepper. Mix until fully incorporated.
Mix in Lions Mane mushrooms, then mix in your Panko breadcrumbs. This mixture will make about 3-4 equal sized round, flat Patties (about ½-3/4 inch thick). Make your tartar sauce (mix all ingredients together and put in fridge until ready to serve).
Heat oil in sauté pan (or heat up your grill and place your grill mats). Cook patties for about 2-3 minutes per side (until they are golden brown and cooked all the way through). Add your garnish of lemon wedges, squeeze on top and enjoy!