Combine all the chicken tikka ingredients and marinate in the fridge for at least 1 hour.
Skewer the marinated chicken pieces on bamboo skewers, then place them over a baking tray lined with parchment paper, making sure there is space underneath the chicken to help distribute the heat more evenly.
Reserve the chicken tikka marinade for later use.
Bake the chicken skewers for about 15 minutes, until slightly dark brown on the edges and cooked throughout.
Heat oil in a large pot over medium heat, then sauté the onions with the herbs and spices until just browned.
Add in the chopped tomatoes and fry till soft.
Pour in the yogurt, water, and reserved tikka marinade, and mix it well with the vegetables and spices.
Bring the mixture to a boil, add in the chicken and cook for a further 4-5 minutes. Set aside.
In a large pot, assemble your biryani in the following layers: ⅓ rice, ½ chicken curry, ½ caramelised onion, ½ coriander, ⅓ rice, oil, ½ of the saffron-infused water, ½ chicken curry, ⅓ rice, the rest of the saffron-infused water, ½ caramelised onion, and finally top with the remaining coriander.
Simmer the biryani over a low heat for 10 minutes or until all the water is absorbed and the rice and chicken are heated throughout.