If not done already, bake the potatoes, cool them, then peel them and dice them. Not super small, but not very big either.
In a sauce pan over low heat, melt butter and then add flour. Stir until smooth. Cook 1 minute stirring constantly.
Add milk slowly. Cook over medium heat, stirring often until thick and bubbly.
Add potatoes, salt & pepper, 2 tablespoons of the green onions, 1/2 of the bacon and 1 cup of cheddar cheese. Cook until heated through.
Stir in sour cream. Add in more milk if too thick.
Serve with cheese, bacon pieces and green onions on top.