Heat a dutch oven or soup pot over medium/high heat and melt in 6 Tbsp butter. Add chopped onion, chopped celery, and sliced carrots and sauté for 5-7 minutes, stirring occasionally, until softened and lightly golden.

Add sliced mushrooms and garlic and sauté for another 5 minutes, stirring occasionally until softened.

Add 1/3 cup flour and stir constantly for 1 minute until golden.

Add 6 cups chicken stock, sliced potatoes, 3 1/2 tsp salt (or to taste), and 1/2 tsp black pepper. Bring to a boil, then reduce heat to a simmer, partially cover and cook for 12-15 minutes or just until potatoes are tender.

Add shredded chicken, frozen peas, frozen corn, 1/2 cup heavy whipping cream, and 1/4 cup parsley. Bring back to a simmer and continue to cook for another 5 minutes or until peas and corn are tender. Season to taste with salt and pepper and remove from heat.