Put the flour, sugar and salt in a bowl and gradually mix in the water with your hands forming a stiff dough. Knead for a few minutes, cover with plastic wrap and leave to rest for about 30 minutes.
Divide the dough into a few pieces, each about the size of a slice of bread so it is easier to work with. Take the first piece and roll it out using a rolling pin, fold it and roll out again until the sheet is 1 mm in thickness.
Begin rolling the sheet up from one of the short edges, gently stretching it longer and wider as you do so, until you have formed a cigar. Coat with margarine. Repeat with the rest of the dough.
Cover with plastic wrap and refrigerate for at least an hour.
Preheat the oven to 180 degree C. Cut the chilled pastry into 1.5 to 2 inch cigars with a knife. Use your fingers to massage a little margarine onto the cigars and gently twist out to form a spiral.
Place them on a tray lined with baking paper. Bake for 25 to 30 minutes, until crisp and golden. Sprinkle castor sugar before serving.