For the baked cod, divide the fish fillets into equal-sized pieces. Remove any remaining bones with tweezers. Season with salt and sprinkle with a little lemon juice.
For the breading, place flour and breadcrumbs in shallow bowls. Whisk the egg and add a dash of mineral water (or carbonated soda) if desired.
Dredge the fish in flour, egg and breadcrumbs in order.
In a shallow pan, heat 2-3 fingers of oil and slowly fry the breaded fillets until golden brown.
Drain on paper towels and serve the baked cod garnished with lemon slices.