Good-Cooking - Blue Cheese Potato Salad

Ingredients

• 2 1/2 pounds potatoes, cooked and cubed
• 3/4 cup chopped scallion (green and white parts)
• 3/4 cup chopped celery
• 3/4 cup sour cream (regular or fat-free)
• 1/4 cup mayonnaise (regular or reduced-fat)
• 2 tablespoons minced fresh parsley
• 1 tablespoon white wine vinegar or cider vinegar
• 1 1/2 teaspoons salt
• 1/4 teaspoon pepper
• 1/4 teaspoon celery seed
• 1/2 cup crumbled blue cheese plus extra for top