To prepare the starter dough: Combine the flour, sugar, yeast and water in an airtight plastic container. Mix well and close the lid. Leave aside to proof for 7-8 hours.
To make the dough (B): Sift the high-protein and plain flours together and combine with the sugar and prepared starter dough in a food processor. Pour in water and mix for 4-5 minutes.
Add shortening and continue to mix for a further 4-5 minutes, then cover the mixing bowl with a damp tea towel. Leave aside to proof for 25-30 minutes.
Combine baking soda and ammonia with a tablespoon of water. Stir well and add to the dough. Knead well to blend until dough is smooth and pliable.
Mix ingredients (C) together. Put on a lightly floured working surface and roll out into a thin sugar sheet.
Place the well-proofed dough on a lightly floured tabletop and roll into a rectangle. Lightly brush with a little more water and place the sugar sheet on one side of dough. Bring the other end over to cover. Cut horizontally into 3 equal parts, then cut each part into 4 equal parts.
Make a hole at one end of the corner using a chopstick. Turn the edge of the dough through the hole.
Leave the dough aside to proof for 20-25 minutes. Deep-fry the pieces in medium hot oil until lightly golden and well puffed up.