In a large bowl, mix together Greek yogurt, lemon juice, ginger-garlic paste, turmeric, garam masala, cumin, coriander, smoked paprika, chili powder, and salt. Add chicken breasts or thighs, ensuring each piece is well-coated. Cover the bowl with plastic wrap and refrigerate for at least 1 hour, allowing the flavors to meld beautifully—overnight is best for enhanced taste.

Preheat your grill pan or skillet over high heat. Remove the marinated chicken from the fridge and sear on both sides for 4-5 minutes until charred and cooked through. Alternatively, you can bake the marinated chicken on a parchment-lined baking sheet at 400°F for 15-20 minutes.

In a large saucepan, heat butter or ghee over medium heat. Add finely chopped onions and sauté until golden and translucent—about 5-7 minutes. Stir in minced garlic and additional ginger, cooking for another minute until fragrant.

Sprinkle in the remaining dry spices (turmeric, garam masala, cumin, coriander, paprika, and chili powder) and sauté for 30 seconds to release their oils. Next, pour in the crushed tomatoes, stirring to combine. Let this simmer on low heat for about 10 minutes.

Once the sauce has thickened, stir in the heavy cream or coconut milk and sugar, if using. Let it simmer gently for another 5 minutes, adjusting seasoning with salt and pepper to taste.

Add the seared chicken pieces to the sauce, allowing them to simmer together for 5 minutes. Squeeze in some extra lemon juice and garnish with fresh cilantro before serving hot over steaming basmati rice or with warm naan.