Makeover Sour Cream Potatoes

Ingredients

• 2-1/2 pounds potatoes, peeled and cubed
• 1 cup finely chopped celery
• 1/4 cup finely chopped onion
• 2 tablespoons butter
• 1/4 cup all-purpose flour
• 1 teaspoon salt
• 1/4 teaspoon ground celery seed
• 1/4 teaspoon pepper
• 1 cup fat-free milk
• 1-1/2 cups reduced-fat sour cream
• 1 cup shredded reduced-fat cheddar cheese, divided
• 2 ounces cubed reduced-fat process cheese (Velveeta)
• 4 tablespoons minced chives, divided