• Preheat your oven to 240°C/220°C fan/gas mark 9.
• Chop the potatoes lengthways into 1cm slices, then chop into 1cm chips (peeling optional).
• Pop the chips onto a large (lined) baking tray. Drizzle with oil then season well with salt and pepper. Toss to coat and spread out in a single layer. 
• When the oven is hot, bake on the top shelf until golden, 25-30 mins. Turn halfway through.

TIP: Use two baking trays if necessary.

• Meanwhile, thinly slice the tomato.
• Finely chop the mushrooms (if you've got one, you can also use a blender).
• Drain and rinse the kidney beans in a sieve.
• In a large bowl, mash the beans into a paste with a fork or potato masher.
• Mix the aioli and mustard in a separate bowl.

• Add the mushrooms, BBQ rub, soy sauce, breadcrumbs and ¼ tsp salt (double for 4p) to the bowl with the beans. 
• Using your hands, mix everything together.
• Roll into evenly-sized balls, then shape into 2cm thick burgers—1 per person.

• Place a pan over medium-high heat with a good glug of oil. 
• When hot, fry the burgers for 5-7 mins, carefully turning every 1-2 mins. Adjust the heat if necessary.
• Remove the pan from the heat and sprinkle the cheese on top of the burgers.
• Cover with a lid or some foil to allow the cheese to melt.

• Meanwhile, pop the brioche buns, cut side-up, onto a baking tray to warm in the oven, 2-3 mins.
• Once toasted, spread a spoonful of mustard aioli on the cut sides of each bun. 
• Top the base bun with a few rocket leaves, sliced tomato and burger patty. Close with the top bun.

TIP: Watch the buns closely when in the oven so they don't burn!

• Plate up your umami bean burger along with the crispy chips.
• Keep any remaining aioli close at hand for dipping.