Heat a large Dutch oven or heavy soup pot over medium-high heat. Add the butter and swirl until melted.

Add the chopped onion, celery, and carrots. Sauté for 5 to 7 minutes, stirring occasionally, until the vegetables are softened and begin to turn golden.

Stir in the sliced mushrooms and minced garlic. Cook for about 5 more minutes until mushrooms release their liquid and brown slightly.

Sprinkle the flour over the vegetables. Stir constantly for about 1 minute so the raw flour taste cooks out and the mixture turns pale golden.

Gradually pour in the chicken stock while stirring to avoid lumps. Add the sliced potatoes, salt, and pepper.

Bring the pot to a gentle boil, then lower the heat to a simmer. Partially cover and simmer for 12 to 15 minutes, until potatoes are tender.

Stir in the shredded chicken, peas, corn, heavy cream, and chopped parsley. Simmer for an additional 5 minutes, until everything is heated through.

Taste and adjust seasoning with extra salt and pepper as needed. Serve hot and garnish with more parsley.