1. In a stock pot, melt butter and add onions until tender. Reduce heat and stir in flour, salt, and pepper and stir until smooth. Slowly add broth and stir. Turn the heat up to med-med high and bring to a boil. Add mushrooms, celery, carrots, potatoes, squash, corn and thyme. Reduce and simmer soup about 30 minutes or until the veggies are as tender as you like.
2. Add cream, parmesan and chicken. Reduce heat and heat the soup about 10 additional minutes without letting it boil.