Prepare pastry baking pan and evenly brush it with a thin layer of margarine. Set aside.
Beat the egg whites, icing sugar and cornstarch until mixture has thickened. Add chocolate paste, stirring until blended.
Add mixture into a pastry bag or a plastic bag with the tip cut off. Pipe the mixture onto a baking sheet, then let stand at room temperature for 10 minutes until the dough is stretched and thin.
Bake in the oven for 10 minutes at 170 C.
Open the door to the oven for 5 minutes; close oven door and bake again for 20 minutes at 120 C until cooked and dry. Remove from oven.
Once cool, sandwich together with two sides with a layer of melted chocolate in between. Sprinkle with toasted cashews. Serve.
