Preheat the oven to 220*.
Put the bite-size cauliflower in a large pan, cover with just-boiled water. Set aside for 5 minutes, then drain and coat in the olive oil and the spices, the garlic and half of the lime juice. Season and spread on a baking tray. Roast for 15 minutes.
Meanwhile, soak the cashew nuts in a cold water for 10 minutes. In a separate bowl soak the red onion in half the remaining lime juice. Heat some oil in a pan and fry the mushroom.
Drain the cashews and whizz in a high-speed blender with the jalapeno, most of the rocket leaves, the rest of the lime juice and 5 tbsp of water, until smooth. And season.
Once cooked through, set aside the mushrooms. Place the tacos on the pan, you might have to do this in several batches. Heat the tacos by leaving them 30sec on each side.
Assemble the tacos: distribute the cauliflower over the tacos, top with mushrooms, cashew sauce, pickled onions and the remainder of the rocket leaves over the tacos. Serve two tacos per person.