Spray the saucepan with low calorie cooking spray. Add the onions, pepper and garlic and sauté over a low heat for 5 minutes until the onions have softened.
Add the mushrooms, chilli powder, paprika, onion granules, mustard powder and coriander to the pan and gently fry for two minutes until the mushrooms have softened.
Add the stock, lentils, black beans, kidney beans, sweetcorn, passata, chopped tomatoes, Henderson's Relish, balsamic vinegar and Marmite. Stir well and simmer over a low heat with the lid off for 20 minutes until the chilli has thickened.
Stir in the tomato puree and season with salt and pepper to taste. Serve on its own or with the side of your choice.