1.Preheat oven to 220°C (200°C fan-forced). Line a large oven tray with baking paper.
2.Toss fish in flour; shake away excess. Coat fish in egg whites, then in combined breadcrumbs, cornflake crumbs, salt and lemon pepper. Place fish in a single layer on the prepared tray; bake for 15 minutes or until cooked through.
3.Meanwhile, combine the mayonnaise and dill in a small bowl.
4.Cut each baguette in half, then slice in half lengthways, not cutting all the way through. Divide the fish, mayonnaise, extra dill and lettuce leaves among baguettes. Serve with a squeeze of lemon.