Heat 1-2 tablespoons of the olive oil in a pan over a medium-low heat and fry the onions for 15 minutes, stirring frequently, or until they are softened and golden-brown.
In a bowl, mix together the cooked onions, tofu, beetroot, mushrooms, carrots, smoked paprika, garlic, thyme and kidney beans. Season, to taste, with salt and freshly ground black pepper.
With damp hands, divide the mixture into approximately 150g/5oz portions and shape into patties.
Heat the remaining olive oil in a frying pan and fry the patties for 3-4 minutes on both sides, or until golden-brown. Heat a griddle pan until smoking, then add the patties and fry for a further 1-2 minutes on both sides, or until there are deep char lines on both sides.
To serve, place the patties into burger buns and arrange over the toppings of your choice.