Remove the crusts from the bread slices. These can be used for making breadcrumbs so as not to waste them. If left on, the crusts will burn upon frying, so do not omit this step. Cut the slices into 4 squares. Then, cut each square diagonally to make 2 triangles. This will give you 8 triangles per slice of bread. Lay the bread triangles on a tray and leave them on the counter to air-dry for about 2 hours or more. This helps age the bread making it more solid. Bread that is too soft will soak up too much oil during frying.
Whilst the bread triangles are drying, wash and pat dry the prawns. Put them in a bowl and add the soy sauce, salt, sugar, ginger, garlic, cumin, chilli powder, pepper and lemon juice. Mix well and let the prawns marinate for 20 minutes in the fridge.
Divide the egg white into two portions. Add half a tbsp of the cornflour in one portion and mix it with a spoon until combined. Set aside.
Put the remaining half of the egg white, remaining half tbsp of cornflour and the marinated prawns in a processor. Process until you have a some-what fine paste. If you do not have a processor, simply chop up the prawns and crush them with either a pestle or the flat side of a knife and then mix them in the other ingredients. Fold in the chopped coriander.
Brush the bread triangles first with the egg-white+cornflour mixture, then pile a small amount of the prawn paste and smooth it to the edges of the triangle. Sprinkle some sesame seeds if you want. Repeat until all the triangles are done.
Heat oil on medium, then deep-fry the bread triangles (prawn side up first) for about 2 minutes or until golden, then flip them and fry the other side. Do not crowd the frying pan. Remove with a slotted spoon and drain out all excess oil on crumpled kitchen towels. Continue until all are done. You can keep them warm in a preheated oven at low temperature until all the prawn toast are done. This helps remove excess oil too. Serve warm with a dip of your choice.
Although the authentic method of preparing these is deep-frying, you can also bake these yummy treats instead. Simply pre-heat the oven at 180 C and bake them on a greased tray until the toast is golden and crisp.