Peel and chop potatoes. Boil in lightly salted water until soft. Drain and set aside.
While potatoes are boiling, chop onion, celery, and garlic. Saute in a large pan/soup pot over medium heat in butter and olive oil.
Once vegetables are soft, add flour and stir for about a minute. Add 1 cup of milk, reducing heat to low, and stir until smooth. Add stock and wine and bring to a boil.
Add 3/4 of cooked potatoes to soup. Puree with an immersion blender if desired. Add remaining potatoes and bay leaf. Salt and pepper to taste. Simmer for an additional 10 minutes.