Preheat and Prepare: Preheat the oven to 350°F. Place the unsalted butter in a 9x13-inch baking dish and allow it to melt in the warming oven.

Layering: Once the butter has melted completely, remove the baking dish from the oven. Arrange the shredded chicken evenly over the melted butter in the dish. Next, distribute the frozen peas and carrots evenly over the chicken layer. Season the entire dish with kosher salt, freshly ground black pepper, and garlic powder.

Preparing the Biscuit Layer: In a medium-sized mixing bowl, combine the Red Lobster Cheddar Bay biscuit mix with the milk until the mixture is well blended. Pour this biscuit mixture evenly over the chicken and vegetable layers in the baking dish. Be careful not to mix the layers together.

Adding the Creamy Sauce: In the same mixing bowl (now empty), whisk together the cream of chicken soup and chicken stock until the mixture is smooth and well combined. Carefully pour this creamy mixture over the biscuit layer in the baking dish, ensuring that it covers the entire surface evenly.

Baking: Place the assembled casserole dish, uncovered, into the preheated oven. Bake for approximately 45-50 minutes or until the top layer of biscuits is golden brown and the sauce beneath has thickened to a gravy-like consistency.

Rest and Serve: Once fully baked, remove the casserole from the oven and allow it to cool for about 15 minutes before serving. This resting period allows the flavors to meld together and the dish to set properly.