Chocolate Pastry Balls (bossche Bollen)

Preheat oven to 180ºC on conventional bake, not fan-forced.
Place milk, water and butter in a small saucepan and bring to a boil over medium-high heat. Reduce heat to low, sift in flour and mix well with a wooden spoon until smooth. Remove from heat and add the eggs, one at a time, making sure each egg is totally incorporated before adding the next one. Add the salt and sugar, mix to combine.
Transfer the dough to a piping bag with a large round nozzle. Line an oven tray with baking paper and pipe 5cm balls leaving the nozzle inserted just below the surface whilst piping and lifting the nozzle as the ball gets bigger, so it forms a smooth ball shape. Brush with egg wash, making sure there are no pointy bits left on the dough. Bake for 30-40 minutes or until golden and puffed. Make a hole on one side with a chopstick and place back in the turned-off oven until the oven has cooled to dry out the inside.
Using an electric beater, whip the cream with the icing sugar until firm peaks form. Spoon into a piping bag with a small nozzle, and pipe in as much whipped cream as possible through the hole in the side.
Half-fill a medium-sized saucepan with hot water, off the heat. Place chocolate into a heat-proof bowl and sit on top of the saucepan. Stir occasionally until chocolate has melted. Hold onto a filled choux puff at the base while dipping the top into the melted chocolate. Stand, top up on a cake rack to let the excess chocolate drip off. Repeat with remaining puffs.