Heat the oil in a pan and gently fry the onion and garlic for 5 minutes.
Place the mushrooms in a food processor and blitz until fine. Add the mushrooms to the onions and fry for 3 minutes.
Mash the beans with a fork or blitz in a food processor. Transfer the mushroom mixture to a mixing bowl and stir in the miso paste, mashed beans, parsley, salt and pepper, cayenne pepper, Parmesan cheese, mashed potatoes, bread crumbs and eggs.
Mix well together and shape the mixture into patties and place in the fridge for 30 minutes to firm up.
Heat some coconut oil or avocado oil in a shallow pan and pan fry the patties for 3-4 minutes per side.
Alternatively, arrange the patties on a greased baking sheet and bake at 180°C for 15 – 20 minutes.