Heat the oven to 250F.
In a medium bowl, whisk together the ingredients for dusting the fish and set aside. Then, in a separate medium bowl, whisk together the dry batter ingredients: garlic powder, flour, cornstarch, salt and old bay. When well mixed, add the egg and the beer and whisk gently until just combined. Allow the batter rest 10 minutes before battering the fish.
While the batter rests, prepare the oil. Add 1” of oil to a heavy bottomed pot or pan (I use a dutch oven) and bring to 365F over medium-high heat.
When the oil is hot, batter the fish just before frying. (Remember not to crowd the pot: fry the fish in batches, about 2 pieces of fish at a time.) To batter, pat the fish dry all over, coat in the flour mixture, then dip into the batter. Immediately lower the battered fish into the oil gently and fry for a few minutes per side until dark golden brown. Transfer the fish to a wire rack and place in the 250F oven to keep warm while you cook the rest of the fish. Enjoy as soon as possible with chips, lemon wedges, malt vinegar, tartar sauce, and cocktail sauce!