Old Fashioned Potato Soup

Bahan-bahan (12 porsi)

• 5 pounds potatoes (scrubbed, peeled, and chopped into 1-inch pieces)
• water
• 6 cups whole milk
• 1½ teaspoons kosher salt (adjust to taste)
• ½ teaspoon freshly ground black pepper (adjust to taste)
• 2 tablespoons butter (optional)