Preheat oven to 375°F. In a very large, shallow pan, heat the oil and add the ground beef. Use a metal pancake turner to press the beef down into a single layer that covers the entire surface of the pan. Cook for 5 to 7 minutes until browned, then use the pancake turner to flip the beef over and cook for another few minutes. Use a large spoon to spoon out excess liquid, until only a small amount remains. Add onion, garlic powder, onion powder, salt, pepper, and tomato paste to the beef. Stir and cook for 1 minute. Add marinara sauce and heavy cream and remove from heat. Stir in 1 cup of shredded cheese and spoon the beef mix into a large casserole dish. Top with remaining cheese and bake about 10 minutes until the cheese is bubbling and melty. Top with chives and serve immediately.