Shell and devein prawns, leaving tails intact. Gently flatten prawns.
Combine egg and cornflour in small bowl, add prawns. Mix well; coat prawns completely.
Remove crusts from bread, cut slices in half.
Place 1 prawn, cut-side-down on each piece of bread, gently flatten prawns on bread with palm of hand.
Brush with left-over cornflour mixture.
Chop egg yolk and ham into 1cm cubes. Push a cube of egg yolk onto prawns bear tail.
Place a cube of ham in centre of each prawn.
Place ¼ tsp finely chopped shallot at the bottom of each prawn; there should be egg, ham, and shallot along the centre of each prawn.
Gently ease toasts, 2 or 3 at a time, into hot oil, deep-fry until bread is golden and prawns are cooked through; drain on absorbent paper.