A Saskatchewan favorite!
Melt butter in stock pot over medium heat. Add onion and celery. Sauté until slightly soft and translucent, about 6-8 minutes. Sprinkle flour into pan, whisking until slightly clumpy. While stirring, add chicken broth. Stir until well blended and bring to a soft boil over medium heat. Reduce heat to a light simmer until thick, about 7 minutes. When broth is thicken stir in mushrooms and bring to a soft boil. Reduce heat to low, cover and lightly simmer 15 minutes. When ready to serve, whisk in cream. Add salt and pepper and 1 1/2 cups of cheddar. Stir until well blended and cheese is melted. Remove from heat. Ladle into hollowed out large sour dough rolls. Sprinkle with remaining cheese and green onion.