Chicken shawarma sandwich with mango dressing

Ingredients

• 1 kg chicken breasts
• 1 flatbread
• 1 tsp garlic powder
• 2 cloves
• 1 tsp ground turmeric
• 1 tbsp ground coriander
• 1 tbsp ground cumin
• ½ tsp ground cardamom
• ½ tsp cayenne pepper
• 2 tsp smoked paprika powder
• 2 tsp salt
• 3 tbsp vegetable oil
• 1 mango
• 1 tsp tahini
• 2 tbsp lemon juice
• 4 tbsp yogurt
• 1 head iceberg lettuce
• 1 cucumber
• 3 tomatoes
• 1 red onion
• 100 g jarred black olives
• pickled chilli peppers (optional)