Radish Vichyssoise

Ingredients

• 1 tablespoon butter
• 1 1/2 cups thinly sliced onion
• 20 radishes, halved (about 1 pound)
• 1 1/2 pounds baking potatoes, peeled and cut into 1-inch pieces
• 3 cups fat-free, less-sodium chicken broth
• 2 cups 2% reduced-fat milk
• 3/4 cup reduced-fat sour cream
• 1 teaspoon salt
• 1/4 teaspoon black pepper
• 1/8 teaspoon ground nutmeg
• 1/4 cup chopped fresh chives
• 2 radishes, thinly sliced (optional)