In a large-sized bowl, add the beans, potatoes, spinach, mushrooms, and seasoning and with your hands, mix until well blended.
Make 4 equal-sized patties from the mixture.
Grease the Air Fryer Basket with cooking spray and then slide inside.
Adjust the temperature of Air Fryer to 370 °F to preheat for 5 minutes.
After preheating, arrange the patties into the greased Air Fryer Basket in a single layer.
Slide the basket into Air Fryer and set the time for 19 minutes.
After 12 minutes of cooking, flip the patties.
After 19 minutes of cooking, Adjust the temperature of Air Fryer to 90 degrees F for 3 more minutes.
After cooking time is finished, remove the patties from Air Fryer and place onto a plate.
Spread ketchup on the bottom half of each bun.
Place 1 lettuce leaf on the bottom of each bun.
Top each with 1 patty, followed by tomato and onion.
Cover each with top buns and serve.