Dredge fillets in flour seasoned with salt and pepper. Melt butter in a cast iron pan over medium heat. Add olive oil, and heat. Add gar fillets and brown quickly, about 1 minute on each side. Pour hot water into a soup pot. Add cayenne, black pepper, salt and thyme. Add potatoes and onions and cook five minutes. Add carrots and cook 10 minutes more until vegetables are tender but not overcooked. Drain; save water in which vegetables were cooked. Place browned gar fillets in a large casserole. Add vegetables, and pour vegetable water over all. Cover and bake in a 350° oven for 45 minutes. Serve hot from casserole.
