Heat the oven to 400 F (200 C).

Scrub the potatoes and prick them in several places. Bake them for about 1 hour, or until they are tender enough to easily pierce with a fork. Let them cool, then peel and dice.

Melt the butter in a Dutch oven or large saucepan over medium heat. Add the flour and cook, stirring, for 2 minutes.

Gradually add the milk and continue to cook, stirring constantly, until the sauce has thickened.

Add the cooked cubed potatoes and green onions. Continue cooking and stirring until the soup begins to simmer. Reduce the heat to low and simmer for 10 minutes.

Add the bacon, 1 cup of cheese, sour cream, salt, and pepper; cook just until heated through and the cheese has melted.

Serve hot, garnished with the remaining cheese and sliced green onion.