Toss the shredded red cabbage, lemon juice and cider vinegar together in a large bowl with some salt and pepper and set aside.
Put the sliced red onion in a sieve and pour over a kettles worth of boiling water. Mix the vinegar, salt and sugar together in a jar and add the onion slices. Add a couple of peppercorns and set aside until ready to use.
Heat a drizzle of oil in a frying pan and add the onion and mushroom and fry for 10 minutes then add all the spices and cook for another minute. While the mushrooms are cooking mix together the soy sauce, chilli sauce, cider vinegar and maple syrup. Add to the mushrooms and cook for another 10 minutes then remove from the heat.
Serve the mushrooms wrapped in the flatbreads with tomatoes, red cabbage, red onion, coriander leaves and garlic yoghurt.
Notes
The nutrition information doesn't include the flatbreads as the info will vary according to whether you use store bought or homemade.