In a medium bowl make batter: combine flour, cornstarch, Corona, Cajun seasoning and salt and pepper. Let sit for about 15 minutes while you prepare slaw and mayo.
Place 1 cup flour in a small bowl.
Heat vegetable oil over high heat in a frying pan.
Pat fish fillets dry with paper towels and dredge in flour then in batter.
Place fillets in hot oil and fry until golden brown.
Remove and drain on wire rack, salt and pepper to taste.
Prepare sandwich: Spread spicy mayo on top and bottom buns, place piece of fish on bottom bun, slaw on top of fish and top with bun.