In a large stock pot or Dutch oven, melt butter over medium high heat. Sauté celery, onion and garlic in butter until soft, about 5 minutes. Stir in thyme and parsley. Sprinkle with flour. Cook and stir another 2 minutes. Stir in corn and potatoes. Add broth, half and half, salt and pepper. Bring to a boil. Reduce heat to simmer. Cook uncovered for 20 minutes until potatoes are tender. Garnish with dried chives if desired.