Prep the chicken: Pat the chicken thighs dry and cut into 1 1/2–2" (3–5 cm) pieces. Drying the meat ensures the marinade clings and helps achieve a good sear — moisture on the surface will steam rather than brown.

Make the marinade: In a bowl whisk together the Greek yogurt, 2 tsp garam masala, 1/2 tsp turmeric, 1/2 tsp cumin, 1 tsp paprika, minced 2 cloves garlic, 1 tbsp minced ginger, lemon juice, 1 tsp salt and freshly ground black pepper. The yogurt's acidity tenderizes the chicken while the spices infuse flavor; keeping the acid moderate prevents the meat from becoming mushy.

Marinate: Toss the chicken pieces in the marinade until thoroughly coated. Cover and refrigerate for at least 1 hour and up to 4 hours (overnight is fine but longer than 12 hours can over-tenderize). Marinating concentrates flavor and begins to break down connective tissue for silky texture.

Cook the rice: Rinse the dry basmati under cold water until runoff is clear to remove surface starch (this keeps grains separate). In a medium saucepan combine 1 1/3 cups dry rice with 2 cups water and 1/2 tsp salt. Bring to a boil, reduce to a low simmer, cover tightly and cook 12–15 minutes until water is absorbed. Let rest, covered, 10 minutes and then fluff with a fork. Resting allows steam to finish cooking the grains evenly.

Sear the chicken: Heat 1 tbsp oil in a large heavy skillet or cast-iron pan over medium-high heat until shimmering. Shake excess marinade from the chicken and add pieces in a single layer; avoid crowding (work in batches if necessary). Sear 2–3 minutes per side until golden (internal temp ~145–150°F / 63–66°C). A quick high-heat sear gives Maillard browning which builds savory flavor; you do not need to cook chicken all the way through here because it will finish in the sauce.

Saute aromatics: Wipe out the pan, add remaining 1 tbsp oil and reduce heat to medium. Add the chopped onion and a pinch of salt; cook, stirring occasionally, until translucent and just lightly browned (~6–8 minutes). Browning the onion adds sweetness and depth that mellows the tomatoes.

Bloom the spices and build the sauce: Add the remaining minced garlic and ginger to the onion and cook 30–45 seconds until fragrant (do not let garlic burn). Stir in the remaining 1 tsp garam masala, 1/2 tsp turmeric, 1/2 tsp cumin, and optional cayenne; cook 30 seconds to bloom those spices — this releases their essential oils and deepens the aroma. Add the crushed tomatoes, scrape up any browned bits from the pan, and simmer for 8–10 minutes to concentrate flavors and reduce raw tomato tang.

Finish the sauce: Reduce heat to low and stir in the heavy cream (or coconut milk) and butter (or ghee). Taste and adjust salt, pepper, or a squeeze more lemon if needed to brighten the sauce. The cream (or coconut milk) softens the acidity of tomatoes and gives the sauce a silky mouthfeel that clings to the chicken.

Combine chicken and sauce: Add the seared chicken pieces into the sauce, along with any resting juices. Simmer gently 6–8 minutes until chicken reaches 165°F (74°C) and sauce is slightly thickened. A gentle simmer prevents the cream from breaking and ensures the chicken cooks through without toughening.

Rest and finish: Remove from heat, let sit 3–5 minutes. Stir in half the chopped cilantro and spoon a little sauce over the chicken. Resting helps the juices redistribute, keeping the meat juicy.

Plate: Spoon 1 cup cooked basmati rice onto each plate, ladle 1/4 of the chicken and sauce over the rice, and garnish with remaining cilantro. Serve hot with lemon wedges on the side if desired.