Pre heat oven to 375.
Wash and roughly chop all veggies. Mince up veggies- onion, mushrooms, carrot and bell pepper using a food processor. Work in small batches, one veggie at a time for best results. You want a small dice- not complete paste. Spread out veggies on parchment paper lined baking sheet and bake at 375 for 20 minutes. You want them to be slightly dried out and soft. If they are still too wet after 20, pop them back in for another 5 minutes.
Drain and rinse 1 can of black beans. Spread them out on a parchment paper lined baking sheet and bake for 20 ish minutes. They will dry out and poof up. make sure they don't get TOO hard.
While you have the food processor still out, throw in the walnuts and sunflower seeds and blend till finely ground. Set aside.
After the minced veggies and beans are baked, take them out of the oven and add them to a large mixing bowl. Add in the rest of the ingredients- ground walnuts/ sunflower seeds, chickpea flour, eggs and seasonings and mix well. If the mixture appears too wet then add a bit more chickpea flour. It should hold together when you scoop it.
Scoop mixture onto parchment paper lined baking sheet and form into 6 patties. TIP- use the ring of a mason jar lid to make easy perfect circular patties.
Drop the oven temp down to 350. Bake for 20 minutes at 350, flipping halfway through. These are best/ firmest after sitting for a bit, even better the next day.