In a Dutch oven or medium stock pot, melt butter. Add celery, onions and leeks and sauté until onions are translucent (5 minutes).
Add mushrooms and garlic and cook until the mushrooms have stewed down.
Add flour and stir until flour is cooked down.
Add chicken stock, corn and thyme. Season to taste. Bring to a boil and then reduce heat and simmer for 15 – 20 minutes. Add in pasta until cooked (~10-12 minutes). Slowly add heavy cream and serve warm.