Preheat oven to 200C. For choux pastry, place water, milk, butter and salt in a medium saucepan over a high heat and bring to the boil. Remove pan from heat and, using a wooden spoon, quickly beat in flour until mixture is completely smooth. Turn heat down to medium, return the pan to the stove and cook for about one minute, beating all the time, or until the mixture comes away from the pan. Take the pan off the heat and gradually beat in the eggs until a smooth dough forms. The mixture should drop from the spoon, not run off it. Cool slightly.

Transfer dough to a large piping bag fitted with a 1.5-centimetre nozzle. Line a large baking tray with baking paper and pipe on 12 eclairs, each about 15 centimetres long. Bake for 10 minutes or until golden-brown, then turn down to 190C for 20 minutes to dry the centre, then transfer to a rack and leave to cool.

For the filling, melt the chocolate in a bowl over a pan of simmering water. Pour the melted chocolate into the pastry cream, mix in cocoa powder and whisk until smooth. When you are ready to fill the eclairs, transfer the filling to a piping bag fitted with a 0.5-centimetre nozzle. Pierce the underside of each eclair four times with the tip of the nozzle, gently squirting a little filling into the eclair each time.

For the glaze, mix the icing sugar with cocoa and water until smooth. Spoon a small amount of glaze on top of each eclair. To serve, place a small amount of floss on top of each eclair and serve immediately.

Pastry cream

Place the milk, vanilla bean and scraped seeds in a medium saucepan and bring to the boil. Place the egg yolks, sugar and flours in a bowl and whisk until well incorporated. Pour half the hot milk onto the egg mixture while mixing gently. Pour back into the saucepan with remaining hot milk, return to a medium heat and cook for 10 minutes, stirring continuously. Take off the heat, remove vanilla bean. Cover with paper to stop a skin forming and cool.

Makes 1 litre