Mix ½ cup of Greek yogurt, 1 tablespoon of lemon juice, half of 2 tablespoons of ginger-garlic paste, 1 tablespoon of oil, and 1 tablespoon of kasuri methi (dried fenugreek leaves).
Stir in half of 1 teaspoon of Kashmiri chili powder, 1 teaspoon of garam masala, ¼ teaspoon of turmeric, 1 teaspoon of ground coriander, ½ teaspoon of ground cumin, and ½ teaspoon of salt.
Add 700g of boneless chicken thighs, cut into bite-size pieces, and coat well. Cover and refrigerate for at least 8 hours, or up to 48 hours.
Preheat the oven to 475°F / 240°C. Thread the chicken onto skewers and bake in a deep, foil-lined pan for 9-10 minutes on each side, until it reaches 165°F / 74°C. Broil briefly, until charred at the edges.
Meanwhile, heat 3 tablespoons of ghee in a large pan over medium heat. Fry 1½ cups of finely chopped onion with 1 teaspoon of salt for 10-12 minutes, until deep golden.
Stir in the remaining ginger-garlic paste until the raw smell goes, then the remaining Kashmiri chili powder, 2 teaspoons of garam masala, 1 tablespoon of ground coriander, and 1 teaspoon of ground cumin.
Add 450g of puréed tomatoes and cook for 7-8 minutes, until very thick. Pour in 1 cup of hot water, cover, and simmer for 12-14 minutes.
Stir in 1 teaspoon of sugar and ½ cup of heavy cream and cook until creamy. Add the chicken, off the skewers, crush in ½ tablespoon of kasuri methi, cover, and cook for 2-3 minutes, thinning with a little hot water if needed.
