Brown the ground beef in a large fry pan over medium high heat for 5 minutes or until cooked almost through. Add the mushrooms, corn kernals, chopped celery, onion and garlic and cook until vegetables are softened. Stir in the diced tomatoes, tomato paste, basil, oregano and red pepper flakes. Season with kosher salt and ground pepper to taste and cook for 15-20 minutes. Stir in cooked rice and chopped parsley and cook for another 5 minutes or until the rice is warmed through.