Mushroom Mince: Blitz dry ingredients (walnuts, salt, cumin and chilli powder) in a food processor until finely chopped, like couscous, but still with some texture - set aside in a bowl.
Blitz vegetables excluding mushrooms (garlic, onion, carrot, celery) until finely chopped, but still with some texture (don’t blend them to a mush) - add to the bowl with the walnut mixture.
Blitz mushrooms until finely chopped, but still with some texture - again, super important not to over blend to a mush. Add back the walnut and vegetable mix to the processor and pulse very lightly to combine.
Heat the coconut oil on high in as wide/big a pan as you have (you need to the surface area), then fry the mushroom mince on high for 5-6 minutes until cooked and starting to get slightly crispy and dry in some areas. Drizzle over the tamari at the end. The larger the pan, the more likely your mince will get dry rather than cook into a stew.
Sour Cream: blend all ingredients in a blender or food processor until silky-smooth, scraping down the inside of the blender a few times to get a smooth consistency. There should be no lumps of cashews remaining and the mixture should be completely smooth like a regular sour cream.
To assemble, serve the tacos as follows: cos lettuce, chopped cabbage, cooked quinoa, mushroom mince, chopped tomato, sliced avocado, chopped coriander, sour cream, and red chilli flakes. Double up your cos lettuce leaves if you like, to prevent the juices spilling out.