Put the roughly chopped mushrooms and beans into a food processor or a blender. If you don't have a food processor or a blender, you can simply mash everything by hand and dice the mushrooms. Blend together.

Put the composition into a bowl and add the rest of the ingredients for the mushroom burger patties. Mix well using a fork.

If you want the burger patties to be easier to shape, leave the composition to rest in the fridge for at least half an hour.

Heat some oil in a large, non-stick pan and add the patties, one by one. Lightly fry them on both sides, until they get a nice crust. Move them on a paper towel.

Assemble the mushroom burgers. Spread a layer of vegan mayonnaise and ketchup on the halved buns. Add lettuce, some tomato, onion and pickles slices, the mushroom burger patty and that's it! Enjoy a delicious vegan mushroom burger!