Over medium heat combine finely chopped mushroom, yellow onion, Worchester, garlic powder, dried parsley, salt and pepper in a skillet. Cook until little moisture remains.

Place mushroom mixture in a large mixing bowl and fold in the eggs, oat flour panko and parmesan cheese. Mixture should be moist and malleable, like ground beef but not too loose. If too wet add a little oat flour until patties are easily formed.

Gently form patties.

Over medium-high heat generously grease skillet and cook patties for 3-5 minutes on each side. Make sure the pan stays liberally greased during cooking. These patties can also be cooked on the grill or a griddle.

Melt swiss cheese onto mushroom patty and place onto bun. Add any favorite burger fixings like caramelized onion, butter lettuce or condiments.