Caramelized Onion and Black Bean Open Burgers with Mushroom Buns

Drizzle the olive oil into a frying pan and place over a medium-high heat

Add the onions and stir as they soften and caramelize

Add the black beans to the onion and season with salt and pepper

Take the pan off the heat and transfer the onion and beans to a bowl

Use a potato masher to mash the beans and onions together

Shape the bean mixture into patties and place them back onto the frying pan with a drizzle of olive oil, and place over a medium-high heat

Cook the patties on both sides until golden

Set the patties aside and place the mush- rooms onto the hot frying pan to cook on both sides

Lay a patty onto each cooked mushroom, place a tomato slice on top, then sprinkle with the dried thyme and a little drizzle of olive oil