In a bowl, combine chicken thighs with salt, garlic powder, sweet paprika, curry powder, and Greek yogurt. Cover and let it sit for 15 minutes.

Heat a large skillet over medium-high heat and add vegetable oil. Once hot, add the marinated chicken, cooking for 8-10 minutes, flipping halfway until golden brown.

In the same skillet, reduce heat to medium and add butter. Add minced garlic and chopped onion, sauté until onions are translucent, about 3-5 minutes.

Stir in tomato sauce and sugar, simmer for 3 minutes. Return the cooked chicken to skillet, then pour in heavy cream and stir until thickened.

Sprinkle in cayenne pepper, garam masala, and black pepper. Simmer for 10 minutes to meld flavors.

Stir in remaining butter until melted. Adjust seasoning and serve hot with fresh parsley if desired.