Preheat the oven to 200℃ and prepare you oven trays.
Place the water and butter in a pot and bring to a rolling boil (a vigorous bubbling boil).
Remove from the heat and immediately add the flour using your dough whisk to beat the mixture until it creates a ball and leaves the side of the pot.
Leave to cool for 5 minutes. This is a good time to make the filling and place in the fridge to set.
Once the mixture the pot has cooled add the eggs one at a time. Beating well after each addition (the mixture should ball and leave the pot sides before adding the next egg.It's a good arm workout! The mixture is ready when you hold it up to the light and see a smooth glossy texture.
Depending on what size puff you desire - use either pudding spoons or teaspoons to spoon the mixture onto lined trays.
Dip your spoons into a cup of cold water every now and then to stop the mixture sticking to your spoon.
Bake for 30 minutes (set your timer) at 200℃.Then turn down to 100℃ for a further 15 minutes. Remove from the oven and rest on the tray for 5 minutes.Then transfer to a cooling rack and poke a hole in the bottom of each puff. You want your hole to be about 1cm in circumference (big enough to stick the piping tip into). Leave to cool until completely cold to touch and prepare the topping.