Preheat the oven to 375°F (190°C).
Melt butter in a skillet over medium heat. Stir in flour, salt, pepper, garlic powder, and onion powder. Cook 1–2 minutes until bubbly and slightly golden.
Slowly whisk in chicken broth and milk. Cook 3–5 minutes until thickened.
Stir in chicken, peas, carrots, and corn. Remove from heat.
Pour mixture into a greased 9×13-inch casserole dish. Spread evenly.
Flatten biscuits slightly and arrange on top of filling, leaving space between them.
Bake for 25–30 minutes, until biscuits are golden brown and cooked through.
Let sit 5 minutes before serving.