In a large bowl, combine Greek yogurt, lemon juice, ginger-garlic paste, turmeric, garam masala, cumin, coriander, smoked paprika, chili powder, salt, and oil. Cut the chicken breasts into bite-sized pieces and add them to the marinade, ensuring they are well-coated. Cover the bowl and refrigerate for at least 1 hour, but overnight is preferable for maximum flavor absorption.

Preheat your grill pan, skillet, or broiler over medium-high heat. Remove the marinated chicken from the fridge and carefully place it on the hot surface. Sear the chicken for 4-5 minutes on each side until it is well-charred and fully cooked, reaching an internal temperature of 165°F. Alternatively, bake the chicken in a preheated oven at 400°F for 15-20 minutes until thoroughly cooked.

In a large saucepan, melt 2 tablespoons of butter or ghee over medium heat, then add a drizzle of oil. Once hot, add the finely chopped onion and sauté for 5-7 minutes until golden brown. Stir in minced garlic and grated ginger, cooking until fragrant, about 1-2 minutes.

Sprinkle in the remaining spices—cumin, coriander, turmeric, and garam masala—cooking them for about 30 seconds to toast their flavors. Next, stir in the tomato paste, allowing it to caramelize slightly for 1-2 minutes, then add a can of crushed tomatoes. Simmer the mixture over medium-low heat for about 10 minutes to allow it to thicken.

Gradually stir in the heavy cream or coconut milk. Season with salt and pepper to taste. Once the sauce is creamy and well-blended, gently add the cooked chicken, simmering for an additional 5 minutes to meld the flavors.

Add a splash of fresh lemon juice to brighten the dish, and toss in chopped cilantro for freshness. Stir thoroughly before removing from heat. Serve warm, accompanied by fluffy basmati rice or warm naan.