Oyster Mushroom Tacos - Yotam Ottolenghi, Ixta Belfrage

Preheat the oven to 200°C fan. Mix all the ingredients for the pickled onions in a small serving bowl with ¼ teaspoon of salt and set aside. Put all the ingredients for the crema into the small bowl of a food processor, with ¼ teaspoon of salt and 1 teaspoon of water. Blitz until smooth, scraping down the sides of the bowl as you go. Transfer to a small serving bowl and set aside. Mix the kohlrabi with the lime juice and ¼ teaspoon of salt in a small serving bowl and set aside. In a large bowl, mix the mushrooms with the garlic, soy sauce, maple syrup, 75ml of the oil and ¾ teaspoon of salt. Blitz the cumin, cascabel chillies and allspice to a powder in a spice grinder or a pestle and mortar. Put 1½ teaspoons of the spice mix into a small bowl with the remaining 2 tablespoons of oil and set aside, to serve. Add the rest of the spice mix to the bowl of mushrooms. Transfer the mushrooms to two large, parchment-lined baking trays, spread out as much as possible, and roast for 20 minutes. Combine all the mushrooms on one tray, mix well and continue to roast for another 8 minutes, until crisp and browned. While the mushrooms are roasting, make the tortillas. Put the masa harina and a good pinch of salt into a medium bowl and pour in 250ml of boiling water, stirring with a spatula until the dough comes together. Once cool enough to handle, knead into a smooth ball that has the texture of playdough (this should take less than a minute). The dough shouldn’t be wet or come off in your hands, so you may need to add another 10 to 20g of masa harina depending on the brand you are using, as they can absorb water differently. Divide the dough into 12 pieces weighing about 30g each. With lightly greased hands, roll each piece into a smooth ball. Keep any dough you’re not working with covered with a clean damp cloth. Get a clean tea towel ready and cut out six squares of greaseproof paper measuring 14cm, which you’ll need to help you press the dough. Place a large, non-stick frying pan on a high heat. Place one piece of dough between two sheets of paper, then, using a heavy-based pan (or a tortilla press, if you have one), press down evenly and firmly on the dough to spread it out into a circle 10 to 12cm wide. Remove the top sheet of paper and use the bottom sheet to transfer the tortilla to the hot pan. Cook for 90 seconds until nicely browned, then flip and cook for another minute to brown the other side. Transfer the cooked tortilla to the tea towel, fold it over to cover, then repeat with the remaining dough (cook as many tortillas at a time as will fit in the pan). Warm the mushrooms in a hot oven for a few minutes if they have cooled, then pile on to a large platter and drizzle over the chilli oil you set aside earlier. Serve with the tortillas, lime wedges, crema and pickles (discarding the tea bags from the onions) alongside.