In a large heavy saucepan, fry the bacon over medium heat until crisp and then drain on paper towels. Reserve 2 T of fat in the pan and saute onions, celery and potatoes until onion is softened, about 5 minutes.Stir in chicken broth and bring to a boil. Simmer, covered, until the potatoes are almost tender, about 10 minutes.
Add milk to the pan, bring to a boil and simmer uncovered until potatoes are very tender, another 10 minutes. Using a stick blender or a food processor, blend the soup until it is creamy and only a few small chunks of potatoes remain. Stir in salmon, dill and butter and continue to simmer until the fish is cooked through, about 5 minutes.Serve in bowls topped with bacon ( and maybe a little cheddar cheese)