Cook bacon in a Dutch oven until crispy. Remove and set aside. Leave about 2 tablespoons of bacon grease in the Dutch oven and cook onion until soft.
Add potatoes and water. Cover and simmer for 10 to 15 minutes, until potatoes are soft.
Add soup, sour cream, milk, salt, pepper and crushed pepper flakes.Crumble the bacon and add 3/4 of it. (Save rest for garnish.)Bring to a simmer, but don't let boil.Ladle into bowls, sprinkle with crumbled bacon and green onions and Serve.
Notes
Instead of russet potatoes, you can use red potatoes or yukon gold potatoes. Potatoes should be cut into 1/2 to 3/4-inch pieces. If using russet potatoes, peel them. Red potatoes and yukon gold do not need to be peeled.