Spray a 9×13 pan with nonstick spray.
Preheat the oven to 375°F degrees.
Place the biscuits on a baking sheet and bake for 8 minutes. Remove from the oven but leave the oven on.
While biscuits are pre-baking, in a large skillet over medium-high heat, melt the 2 tablespoons of butter.
Add the frozen vegetables and cook for 10 to 15 minutes.
Add the chicken, milk, cream of chicken soup, and salt and pepper to taste. Stir to combine and heat for 5 minutes until the mixture is fully heated and bubbly hot.
Pour into the prepared baking dish and spread evenly.
Take the pre-baked biscuits and place them on top of the casserole with the baked side down and the raw side up.
Place the 2 tablespoons of melted butter in a small covered microwaveable dish along with the garlic powder. Microwave in 30-increments until melted.
Pour the melted butter over the top of the biscuits.
Place the casserole in the oven and bake for 10 to 12 minutes, then tent with foil and bake for an additional 10 to 12 minutes or until the biscuits are golden brown.