Melt butter in a large pot over medium heat.
Add onions, celery, garlic, salt and pepper. Sauté until onions begin to brown.
Gradually add flour to onion mix, stirring constantly.
Add stock a little at a time, stirring constantly.
Add mushrooms and potatoes; simmer until mushrooms are cooked, stirring as needed.
Add cream once mushrooms are cooked. Serve.
