In a large mixing bowl, combine the boneless chicken pieces with all the marinade ingredients: yogurt, lemon juice, garlic, ginger, garam masala, paprika, turmeric, and salt. Mix everything thoroughly to coat the chicken evenly.
Cover the bowl with a lid or plastic wrap and refrigerate for at least 1 hour—or ideally overnight. This allows the chicken to absorb all the flavors and become tender.
Heat 1 tablespoon of oil and 2 tablespoons of butter in a large skillet over medium-high heat.
Once hot, add the marinated chicken pieces in a single layer (work in batches if needed).
Cook for 4–5 minutes on each side, or until the chicken is nicely browned and fully cooked through. Remove the chicken from the pan and set it aside on a plate.
In the medium dutch oven , melt another 2 tablespoons of butter over medium heat along with 2 tablespoons of oil.
Add the finely chopped onion and sauté for about 5–7 minutes, until it's soft, translucent, and golden brown.
Add the minced garlic, grated ginger, and all the spices—including garam masala, cumin, chili powder or paprika, coriander, turmeric, fenugreek leaves, and salt.
Stir constantly and cook for 1–2 minutes until fragrant. Add the tomato paste and stir for a couple more minutes.
Pour in the tomato puree and mix well to combine with the onion-spice mixture. Let it cook for 5–6 minutes, stirring occasionally, until the butter chicken sauce darkens slightly in color and thickens.
The mixture will turn too thick, add ½ cup of water to loosen it to a smooth consistency.
Return the cooked chicken (along with any juices) to the pan.
Stir to coat the chicken thoroughly in the buttery tomato sauce.
Simmer on low heat for 5–7 minutes, allowing the chicken to absorb the sauce and the flavors.
Lower the heat to medium-low, then pour in the heavy cream and sugar (if using).
Stir gently until the sauce becomes rich, smooth, and creamy. Let it simmer for another 2–3 minutes to bring everything together. Turn off the heat and sprinkle with chopped fresh cilantro.
Serve hot with naan, jeera rice, or basmati rice for a comforting and satisfying Indian meal alongside some lime wedges or lemon wedges.