Heat a dutch oven or soup pot over medium/high heat and melt in 6 Tbsp butter. Add onion, celery, and carrots; sauté for 5-7 minutes, stirring occasionally, until softened and lightly golden. This base of sautéed vegetables is crucial for developing a deep, savory flavor.

Add mushrooms and garlic; sauté for another 5 minutes, stirring occasionally until softened. The mushrooms should release their juices, adding to the overall depth of the soup.

Add flour, stirring constantly for 1 minute until golden. This step helps thicken the soup and gives it that classic pot pie consistency. Be sure to cook the flour thoroughly to eliminate any raw taste.

Add chicken stock, potatoes, salt, and pepper. Bring to a boil, reduce heat to a simmer, partially cover, and cook for 12-15 minutes or until potatoes are tender. The potatoes should be soft but not falling apart.

Add chicken, peas, corn, whipping cream, and parsley. Bring back to a simmer and cook for another 5 minutes or until peas and corn are tender. Season to taste with salt and pepper and remove from heat. The cream will add a silky texture, making the soup rich and comforting.