Into a bowl, add the sour starch, add half of the hot water, half of the oil, half of the milk and mix very well. Add the rest of the water, the rest of the oil and the rest of the milk and mix, add the egg and mix.
Add salt and mix well.
Put this mixture into a thick pipping bag, cut the tip and use it to shape the biscuits in a baking tin. You don't have to grease the baking tin.
Bake in a preheated oven at 200°C (392°F) for 15 to 30 minutes or until golden brown. Serve.