Melt butter in large saucepan over medium heat. Add onion and chopped celery. Cook until the onions start to become translucent. Add the carrots and green beans and cook for another 3-5 minutes. Add the garlic and cook for 1 minute. Add the onion powder, parsley and pepper and cook for 30 seconds or so. Add the chicken broth and turn to simmer. Cook about 25-30 minutes or until the carrots and green beans are tender.
Add the noodles and chicken and simmer for an additional 10-12 minutes or until noodles are tender.
Melt butter in microwave and blend in flour creating a roux. Slowly add this to the soup a little at a time whisking well each time. Keep whisking until it is all blended. Add salt to taste and serve.