Do some prep for your burgers. Roughly chop the flat leaf parsley and grate the cheddar cheese.
Tip the cans of drained and rinsed kidney beans into a food processor with the marmite, egg, wholegrain mustard and brown sugar and whiz to form a soft mixture.
Spoon this into a bowl and stir through the parsley, rolled oats and cheese. Leave the mixture to sit for 30 minutes in the fridge to soak up moisture and allow the flavours to develop. Meanwhile, preheat the oven to 200C, fan 180, gas mark 6.
The chilled burger mixture should be thick and pliable. Shape into thick patties, about the size of a digestive biscuit and drizzle the olive oil over the burgers. Rub the patties with the oil so that they are evenly covered.
Fry the burgers in a non stick pan, over a medium high heat for 2-3 minutes on each side, until they are crispy and golden on the outside.
Transfer the burger buns to an oven tray and cover each burger with a slice of cheese. Cook for 10-12 minutes until the cheese has melted and the burger is hot through.
While the burgers are in the oven, slice the avocado and tomato to top the burgers.
Toast the buns in the pan until golden.
Serve the burgers in brioche buns with a squeeze of mayonnaise, sliced tomatoes and sliced avocado