Preheat the oven to 375°F (190°C).
In a large skillet, melt butter over medium heat and sauté diced onion and celery until soft and translucent.
Sprinkle flour over the vegetables and stir continuously for 1-2 minutes to form a roux.
Gradually whisk in seafood broth and heavy cream until smooth and thickened.
Season the mixture with garlic powder, Old Bay seasoning, salt, and pepper, stirring well.
Fold in the chopped shrimp, crab meat, and frozen peas and carrots, then remove from heat.
Pour the seafood filling into a 9-inch pie dish.
Prepare the Cheddar Bay Biscuits according to package instructions, mixing in shredded cheddar cheese.
Drop spoonfuls of biscuit dough evenly over the seafood filling.
Bake for 30-40 minutes or until biscuits are golden brown and fully cooked.
Let the pot pie cool for 10-15 minutes before serving to allow the filling to set.