Add the cold water, milk, caster sugar and unsalted butter to a saucepan.

Place it over medium-high heat until the butter has fully melted. Stir regularly. Then add the plain flour and also a pinch of salt. Keep the pan on the heat!

Stir fast now until you get a thick and glossy batter that comes away easily from the sides of the pan.

Then take the pan off the heat and put the choux batter aside to cool at room temperature for about 10 minutes until lukewarm. Once the batter has cooled enough, lightly beat the egg and gradually add it to the pan.

Line a baking tray with some baking paper. Fill a piping bag with the batter. Pipe little round dollops onto the tray. Smoothen the top of the dough with a wet finger to make it rounder.

Put the baking tray in a preheated oven at 400°F (200°C) for 30 minutes until the choux are puffed up and golden brown.

Then take them out of the oven. Gently turn the profiteroles over and bake them for another 5 minutes in the hot oven. Once baked, remove the puffs and let them cool at room temperature for 30 minutes. In the meantime you can whip up some cream to fill the puffs with. Melt the chocolate and a drop of cream to dip them in.