Cook the onion and celery in olive oil in a large pot.
When the onion is soft, add potatoes, broth, water to the pot.
Bring to boil and cook until potatoes are tender.
In a sauce pan, make a white sauce by melting butter over medium heat.
Whisk in flour and cook 1 minute.
Whisk in milk.
Add cheese and stir till cheese is melted and sauce is thickened.
Add cheese sauce to broth.
Stir in smoked sausage. Heat soup several more minutes, being careful not to let it boil.
Season with salt and pepper.