1. Line a baking tray with non-stick baking paper and dampen the paper with cold water. This creates steam which helps the bun to rise more. Sift the flour onto a square of baking paper and add the sugar.
2. Put the water in a pan with the butter over a medium heat and stir with a wooden spoon. As soon as the butter has melted and the mixture comes to a boil, turn off the heat immediately, as too much boiling will evaporate some of the water.
3. Tip in the flour and sugar all at once, while beating the mixture vigorously with a wooden spoon. Beat until the mixture forms a smooth ball of paste that leaves the sides of the pan clean.
4. Gradually beat in the eggs, a little at a time, mixing in each addition thoroughly before adding the next, until its a smooth, glossy paste.
5. Spoon the mixture into a piping bag. Pipe the choux pastry onto the baking tray and bake for 20-25 minutes until brown and puffy. Pierce the side of each bun and return to the oven for a further 2-3 minutes to crisp up, then cool on a wire rack.