Preheat the oven to 200 °F. Line a baking sheet with baking parchment or a reusable silicone mat.
In a medium pot over medium heat, add the olive oil. Once hot, add the onion and sauté for 2-3 minutes or until the onion is soft.
1 tablespoon olive oil, 1 onion
Add the mushrooms and cook for 5 minutes, stirring often, until they have released most of their moisture.
150 g chestnut mushrooms, 150 g shiitake mushrooms
Add the vegetable stock and quinoa. Stir to combine then cover with a lid and reduce heat to simmer.
450 ml vegetable stock, 170 g quinoa
Cook for 15 minutes or until the quinoa is soft and tender. Uncover and cook for 5 minutes longer, stirring constantly, to remove any excess water.
Spread the quinoa mixture on a plate and allow it to cool for 5 minutes.
Meanwhile, place the tofu in a nut milk bag or a clean tea towel and squeeze out as much water as you can. Transfer the tofu to a large bowl and mash to a paste with a fork. If using cannellini beans instead, simply drain the can, transfer the beans to a bowl and mash with a fork.
350 g firm tofu
Add the remaining burger ingredients and mash again until combined.
3 tablespoon oat flour, 1 tablespoon dark soy sauce, 1 tablespoon tomato puree, 2 tablespoon fresh parsley, ¼ teaspoon fine sea salt, ½ teaspoon ground black pepper
Make sure no water remains in the pan with the cooked quinoa, then add it to the mashed tofu. Mix well.
Divide the burger mixture into 8 equal portions and shape into burger patties. (Press the mixture into a circular cookie cutter for perfect circular burgers).
Place the burgers on the prepared baking sheet and bake in the oven for 15 minutes then flip and bake for a further 15 minutes. Alternatively, freeze the uncooked burgers until solid then transfer to an airtight container and store in freezer until desired.
While the burgers cook, make the quick ketchup.