In a large bowl, combine the chicken pieces with all the marinade ingredients: yogurt, ginger-garlic paste, turmeric, Kashmiri red chili powder, garam masala, and salt. Mix well to coat. Cover and refrigerate for at least 1 hour or overnight.

Heat oil or ghee in a large, heavy-bottomed pan over medium-high heat. Cook the marinated chicken in batches until golden brown and cooked through. Remove the chicken from the pan and set it aside.

In the same pan, melt 2 tablespoons of butter over medium heat. Add the whole spices (cardamom, cloves, cinnamon stick) and sauté for about 30-60 seconds until fragrant.

Add the chopped onion and cook until softened, about 5-7 minutes. Stir in the ginger-garlic paste and cook for another minute.

Add the crushed tomatoes and raw cashews. Bring to a simmer and cook for 10-15 minutes, stirring occasionally, until the tomatoes have broken down.

Remove the mixture from the heat and let it cool slightly. Discard the cinnamon stick. Transfer the mixture to a blender and blend until completely smooth. For an extra velvety sauce, strain it through a fine-mesh sieve back into the pan.

Return the sauce to the pan over low heat. Stir in the remaining 2 tablespoons of butter, the heavy cream, and the sugar. Crush the kasuri methi between your palms and add it to the sauce. Simmer gently for 5 minutes.

Add the cooked chicken back into the sauce. Stir to combine and let it simmer for another 5 minutes to allow the flavors to meld. Serve hot with naan or basmati rice.