Mushroom doner

Name: Mushroom doner
Prep time: 30 min
Cook time: 30 min
Total time: 1 h
Cuisine: American
Ingredients: 1 x 400g tin chopped tomatoes; 2 tbsp rose harissa; 2 tsp caster sugar; good squeeze lemon juice; 1 onion, very thinly sliced into half moons; 2 level tsp white wine vinegar; 20g/¾oz flatleaf parsley, finely chopped; 150g/5½oz plain yoghurt; 1 heaped tsp dried mint; salt and freshly ground black pepper; 500g/1lb 2oz oyster mushrooms, very thinly sliced lengthways; 2 tsp garlic oil; 2 tsp sweet paprika; 2 heaped tsp ground coriander; 2 tsp celery salt; 3 tsp garlic granules; ½ tsp freshly ground black pepper; 4 white pitta breads; ¼ small white cabbage, very finely shredded; 2 tomatoes, sliced cut into half moons; 4–6 pickled chillies, thinly sliced (optional)