Sift and mix dry ingredients.

Bring water and butter to a rolling boil, remove from heat, immediately tip in dry ingredients, and whisk (U.S. option HERE) to combine.

Return to the heat and keep stirring with a flexible spatula (U.S. option HERE) until the mixture comes away from the sides of the pan and forms a ball (about 1 min).

Transfer it to a Pyrex or similar mixing bowl, and allow it cool, while you pre-heat the oven to 190°C static.

When the mixture is barely warm, add beaten egg(s) a little at a time whilst beating vigorously with a manual balloon whisk until you see trails and the stiff paste very reluctantly drops from a height. You probably won't need the entire beaten egg(s) - check often and stop adding when the paste is a sticky and thick - it needs to be much denser than choux dough made with wheat flour.

Line an oven rack with non-stick parchment paper (don't use a silicone mat).

Scoop the dough into a piping bag and snip the end so as to create a large opening (2.5cm/1”); pipe 6 x 12cm/5" strips, allowing some spacing between them; N.B. If the dough drips out of the piping bag without any pressure, or spreads out once piped, it means you added too much egg - this cannot be salvaged and you'll need to start over.

Bake for 10 minutes, reduce the heat to 170°C static and bake for a further 20 minutes.

Turn oven off, jam the door open with a wooden spoon and leave in situ for another 15 mins.

Remove the baking paper, poke holes on the sides using a skewer, and return the pastries to the oven until cool.

Prepare some very strong coffee - a shot of espresso is ideal; set aside until cold.

Beat mascarpone and icing 'sugar' until creamy and smooth; incorporate the cold coffee.

Add whipping cream and whip using an electric hand-held whisk until you have a thick cream that doesn't slide when you tilt the bowl - careful not to over-whip or you'll end up with butter.

When the pastries are cold, slice them across horizontally, and spoon the coffee cream (or pipe it) equally over the bottom half of each; place the top half over the cream, then leave your éclairs in the fridge while you complete the final step.

Melt chocolate chips over a bain-marie and stir in milk; leave to cool down.

Drizzle over the éclairs and refrigerate.