If the egg yolk is not convex and firm, don't consume the egg.
In a mixing bowl, beat together the dissolved corn flour, egg, egg yolk and salt.
Melt 40g (1½oz) reduced fat margarine with 75g (2¾oz) dark chocolate, cool slightly then beat in an egg yolk.
Brush the pastry case with the egg yolk mixture to glaze the pastry.
Brush with the egg yolk and milk mixture, sprinkle with caster sugar.