Ingredients

• ½ teaspoon unsalted butter
• 1 large white onion, diced
• 2 ribs celery, chopped
• 3 small leeks, cleaned and thinly sliced
• 3 medium potatoes, peeled and chopped
• 3 cups water, or more as needed
• 3 cups 2% low-fat milk
• ½ teaspoon salt
• ½ teaspoon ground black pepper