In a large mixing bowl, combine skinless, boneless chicken thighs with salt, garlic powder, sweet paprika, curry powder, and Greek yogurt. Ensure all the chicken pieces are well-coated in the marinade. Let the chicken marinate for at least 15 minutes for optimal flavor infusion, or refrigerate for up to an hour for even deeper flavor.

Heat 2 tablespoons of vegetable oil in a large skillet over medium-high heat until shimmering. Carefully add the marinated chicken in a single layer, allowing it to sear without overcrowding. Cook for about 8-10 minutes, flipping once halfway, until golden brown and cooked through. Remove the chicken from the skillet and set aside on a plate.

In the same skillet, reduce the heat to medium, and add 2 tablespoons of butter. Once melted, add 3 minced garlic cloves and one finely chopped onion. Sauté this mixture for about 3-4 minutes until the onions become translucent and fragrant.

Next, stir in one cup of tomato sauce and 1 tablespoon of sugar, allowing it to bubble. Reduce the heat slightly and let it simmer for 2-3 minutes while stirring occasionally.

Return the cooked chicken to the skillet, mixing it well with the sauce. Pour in ½ cup of heavy cream, along with ½ teaspoon of cayenne pepper and 1 teaspoon of garam masala. Simmer on low heat for about 10 minutes, allowing the flavors to meld and the sauce to thicken.

Stir in a tablespoon of cold butter to finish. Taste your butter chicken and adjust seasoning as needed. Garnish with freshly chopped parsley and serve hot alongside warm naan and fluffy steamed rice.