Water Dough: Sift flour for water dough and put in a mixing howl. Add sugar, salt and shortening. Slowly add water and mix well to form a smooth and stiff dough. Cover and leave to rest.
Oil Dough: Rub shortening into the flour and mix well to form a soft dough.
Filling: Mix beaten egg mixture with evaporated milk and salt. Add in 400ml cooled syrup and combine well. Strain the custard mixture into a jug and mix well.
Place oil dough inside the water dough. Fold the corners to the middle to enclose the oil dough. Roll out dough on a lightly floured surface.
Fold the sides in to form three layers and seal the edges. Slightly roll out dough. Repeat the folding then roll out flat into a rectangular piece. Use a cutter to stamp out circles of 9-10cm diameter.
Use the pastry to line lightly greased egg tart moulds. Pour in the custard filling.
Bake in a preheated oven at 180 ºC for five to 10 minutes. Cover the tart with a piece of foil and bake for a further 25-30 minutes or until custard is set.