In a large mixing bowl, combine the bite-sized chicken thighs with salt, garlic powder, sweet paprika, curry powder, and Greek yogurt. Ensure the chicken is well-coated with the marinade. Set aside for at least 15 minutes to allow the flavors to meld.

Heat a splash of vegetable oil in a large skillet over medium-high heat. Add the marinated chicken in a single layer. Cook for about 8-10 minutes until golden brown, stirring occasionally. Remove and set aside.

In the same skillet, reduce heat to medium and melt 1 tablespoon of butter. Add minced garlic and diced onion, sauté for 3-4 minutes until onion is translucent and fragrant.

Pour in the tomato sauce and add a pinch of sugar. Stir and let it simmer for 2-3 minutes. Return the cooked chicken to the skillet.

Stir in heavy cream, along with cayenne pepper, garam masala, curry powder, and black pepper. Simmer on low heat for about 10 minutes, stirring occasionally until fully cooked and the sauce is rich and creamy.

Stir in the remaining cold butter until melted for a silky finish. Sprinkle parsley or cilantro on top if desired.

Serve hot alongside warm naan bread and steamed rice.