Place the prawns in a food processor with the ginger, spring onion, egg white, cornflour, sesame oil and soy sauce and whiz to form a thick paste.
Spread the mixture on each of the slices of bread. Place the sesame seeds on a large plate and press the prawn toast, prawn side down, in the seeds to lightly cover.
Heat 2 tablespoons of the oil in a large, heavy-based frying pan. Cook 2 of the prawn toasts, prawn side down first for 1–2 minutes until golden; then turn over and cook the other side for 1 minute until golden. Repeat the process wiping out the pan with kitchen paper and heating the remaining oil first. Drain on kitchen paper, then cut into triangles.
Serve the toasts with plenty of cucumber and sweetcorn salsa (see below), if liked.