Lay the chicken breast flat on a board and cut through the middle carefully so you have two equal-sized, thinner fillets. Cover with a sheet of baking parchment, then gently bash with a rolling pin until around 1/2cm thick.

Put the seasoned flour in a shallow dish, the beaten egg in a second and the parmesan and breadcrumbs in a third, tossing the cheese and crumbs together to combine. Dip one of the thin chicken fillets in the flour, shaking off any excess, then turn to coat in the egg, then finally coat in the breadcrumb and cheese mixture. Repeat with the other piece.

Heat some oil (about 1/2 cm deep) in a large frying pan over a medium heat and cook the schnitzels over a medium heat for 4-5 mins until crisp and golden. Carefully turn and cook the other side for another 4 mins until golden and cooked through. Drain on a sheet of kitchen paper.

Mix the mayonnaise with the chilli sauce, and spread this over two slices of the bread. Put a layer of lettuce on the bottom half of the sandwich, then top with the chicken, cucumber and the remaining bread slices.