In a medium bowl, combine chicken chunks with salt, garlic powder, sweet paprika, curry powder, and Greek yogurt. Mix well until chicken is evenly coated and let marinate for at least 15 minutes while preparing other ingredients.

Heat 3 tablespoons of vegetable oil in a large skillet over medium-high heat. Add marinated chicken and cook for 8 to 10 minutes, stirring occasionally, until golden brown and cooked through. Remove chicken from skillet and set aside, leaving the oil in the pan.

Reduce heat to medium and add 1 tablespoon of butter to the skillet. Scrape any browned bits from the bottom of the pan, adding a splash of water if needed. Add minced garlic and diced onion with a pinch of salt, and saute until onion is translucent and fragrant, about 4 to 5 minutes.

Stir in tomato sauce and sugar. Let simmer for 2 to 3 minutes before adding the chicken back into the skillet. Mix well, then pour in heavy cream and stir until sauce turns a beautiful orange color.

Add cayenne pepper if using, garam masala, curry powder, and black pepper. Let sauce simmer on low heat for 10 minutes, allowing flavors to meld together. Taste and adjust salt as needed.

Stir in remaining 2 tablespoons of cold butter and let it melt into the sauce for a silky finish. Sprinkle with chopped parsley if desired.

Serve hot with naan bread and steamed rice. Enjoy immediately.