Cook celery and carrots in 1 cup chicken broth until soft. Puree with immersion blender.
In a large pot melt 1 tbsp butter and cook onions 2 min. Add the burger and brown until done. Stir in basil, parsley, chicken broth, pureed vegetables and potatoes. Bring to a boil. Reduce heat and simmer until potatoes are done,
In a separate pan add the rest of the butter and stir in flour to make a roux. Slowly add the milk and cook until smooth. Add to soup mixture. Bring back to a boil and reduce heat to simmer. Add the cheese and let it melt stirring occasionally. Lastly stir in the sour cream and heat through