Begin with Butter: Start by melting 6 Tbsp of unsalted butter in a large pot over a medium-high flame.
Vegetable Sauté: Toss in the yellow onion, carrots, and celery into the pot. Stir them around for about 5-7 minutes until they're soft and taking on a golden hue.
Mushroom and Garlic Addition: Add the mushrooms and garlic into the mix, letting them cook together for 5 more minutes until everything is tender.
Thickening with Flour: Sprinkle the flour over the vegetables, stirring it in well for a minute until it forms a golden roux.
Liquid and Seasonings: Slowly add in the chicken stock, followed by the potatoes, salt, and pepper. Bring the mixture to a boil, then drop the heat to a simmer, covering the pot partially. Let it cook until the potatoes are just tender, about 12-15 minutes.
Chicken, Peas, and Corn: Stir in the shredded chicken, peas, and corn, mixing them into the soup thoroughly.
Final Creamy Touch: Add the whipping cream and parsley, bringing the soup back up to a simmer for a few more minutes until the additional vegetables are soft.
Ready to Serve: After adjusting the seasoning to your liking, take the soup off the heat. Ladle it into bowls, garnish with a sprinkle of parsley, and it's ready to enjoy.