Cut a two inch pocket into the thickest part of each chicken breast. Stuff each pocket with spinach and feta cheese and seal with a tooth pick. Season each breast well with salt and pepper. Heat oil over medium high heat and saute the breasts until golden brown on all sides. Remove chicken to a plate and cover with tin foil. Add onion to remaining oil in pan and cook for 2 minutes. Stir in garlic and cook for 30 seconds. Stir in white wine and bring to a simmer. Stir in tomatoes and basil. Bring to a simmer and return chicken to the pan and cover. Simmer for 10 minutes. Remove lid and season sauce to taste. Serve with butter noodles tossed with parsley.