Marinate the chicken: Stir the yogurt, 1 tablespoon ginger, 4 cloves garlic, 2 teaspoons garam masala, turmeric, 1 teaspoon cumin, 1 teaspoon chili powder and 1 teaspoon salt together in a bowl. Add the chicken pieces and turn them until every piece is coated. Cover and refrigerate at least 30 minutes, or up to overnight for the best flavor.

Sear the chicken: Heat the oil and 1 tablespoon of the butter in a large skillet over medium-high heat. Add the chicken in a single layer, working in two batches, and cook 3 minutes per side until browned outside. It won't be cooked through yet. Move it to a plate.

Cook the onion: Lower the heat to medium and add the remaining 3 tablespoons of butter to the same skillet. Add the chopped onion and cook 6 to 7 minutes, stirring, until soft and just starting to brown at the edges.

Bloom the spices: Stir in the remaining ginger and garlic, the 2 teaspoons garam masala, 1 teaspoon cumin, coriander and 1 teaspoon chili powder and cook 1 minute, until the kitchen smells like the whole spice cabinet. Stir the whole time here, because ground spices scorch fast in butter.

Simmer the sauce: Pour in the crushed tomatoes and the 1 teaspoon of salt. Simmer 12 minutes, stirring now and then, until the sauce darkens and thickens enough that a spoon leaves a track across the bottom of the pan.

Add the cream and sugar: Turn the heat to low and stir in the heavy cream and the sugar. Crush the kasoori methi between your palms and add it if you have it. The sauce should turn a soft orange.

Finish the chicken and serve: Return the seared chicken and any juices on the plate to the skillet. Simmer 8 to 10 minutes, until the pieces are cooked through and register 165°F on an instant-read thermometer. Taste for salt, scatter the cilantro over the top, and serve over the basmati rice.