In a bowl, whisk together all the ingredients for the marinade; add the chicken and toss to coat. Let marinate for 1 hour (ideally overnight in the fridge, if time permits.)

Warm oil in a large skillet (preferably cast iron) over medium-high heat. Once shimmering, add chicken pieces in batches, if necessary, making sure not to crowd the pan. Let them fry, untouched, for 1 minute to develop a crust, then saute until browned for about 5 more minutes. Set aside and keep warm.

Melt the butter in the same pan. Saute the onions until soft (about 3 minutes) while scraping up any browned bits stuck on the bottom of the pan. Add ginger and garlic; sauté for 30 seconds until fragrant.

Add in the brown sugar, coriander, cumin, paprika, garam masala, and salt. Stir occasionally for about 15 seconds until fragrant.

Pour in the tomato sauce; let simmer gently for about 3-5 minutes, stirring occasionally until sauce thickens and becomes deeper in color.

Stir in the cream until incorporated.

Add the partially cooked chicken along with its juices back to the pan; cook for an additional 8-10 minutes until chicken is cooked through and the sauce is thick and bubbling. Pour in the water to thin out the sauce, only if necessary.

Serve over cooked basmati rice, with Naan bread, and garnish with chopped cilantro.