Preheat your oven to 400°F.
In a large skillet over medium heat, melt the butter.
Add the diced onion and celery, cooking until softened, about 5 minutes.
Stir in the flour and cook for an additional minute, stirring constantly.
Gradually whisk in the seafood stock and heavy cream, bringing the mixture to a simmer.
Add the seafood mix, frozen vegetables, Old Bay seasoning, garlic powder, salt, and pepper. Cook for 5 minutes until thickened.
Transfer the seafood mixture into a greased 9-inch pie dish.
In a separate bowl, prepare the Cheddar Bay Biscuit mix according to package instructions, adding the shredded cheddar cheese and milk.
Spoon the biscuit mixture over the seafood filling, spreading it evenly.
Bake in the preheated oven for 25-30 minutes, or until the biscuit topping is golden brown and cooked through.
Let it cool for 5 minutes before serving.