In a large Dutch oven, melt unsalted butter and olive oil over medium-high heat. Add sliced cremini mushrooms and sauté until browned.

Reduce heat, add finely chopped yellow onion, and sauté until translucent. Add minced garlic and sauté until fragrant. Stir in flour to form roux.

Gradually whisk in chicken broth, bring to a simmer, and add chicken breasts. Season with salt and simmer until chicken is cooked through.

Remove chicken, shred it, and return it to the pot with the mushrooms.

Stir in heavy cream and heat through. Adjust seasoning and garnish with parsley before serving.