Preheat your oven to 200C (fan). Sift the flour, xanthan gum and salt into a small bowl and set aside.

Add the water, milk, 1 tsp caster sugar and butter to a small saucepan. Heat for a few minutes until the butter has melted and the mixture is bubbling gently.

Tip the sifted flour into the saucepan and stir vigourously to combine (keep the pan over the heat). It will form a sticky ball of dough and you should heat and stir it for a couple more minutes, while squishing and stirring it with a wooden spoon.

Take off the heat and transfer to a stand mixer (or mixing bowl if you prefer to use a hand whisk or arm power!). Mix for a couple of minutes until the mixture has cooled a little and is only warm to touch. This is to ensure the eggs do not scramble when you add them.

Now add an egg and mix until it has been fully incorporated into the dough. Then a second egg and repeat the mixing process.Whisk the third egg in a small bowl and add a little at a time to the mixing bowl. You are aiming for a thick, slightly sticky cake batter consistency, and I find half the third egg is perfect for the Schar flour. If you are using a different flour blend, you may need a little more/less egg, so go steady (and see images below for what you are aiming for). For example, for FREEE flour, I find only two eggs are needed.

Once you've made the dough, use a spatula to scrape it into a piping bag with a round or star nozzle (for a slightly stripy effect). Ensure you are using a nice strong piping bag, as thin plastic ones may not be robust enough.

Place a non-stick piece of baking paper on a baking tray, then pipe lines of choux onto the tray - about 12cm long and 2.5cm wide. Ensure you leave a little space between them, as they will at least double in size during baking.

Wet your finger and wipe down the pointy tip on the edge of each eclair, left over from piping, to give them a nice smooth finish. Place the eclairs into the preheated oven (at 200C fan), then immediately turn the temperature down to 170C fan, and bake for 30-35 minutes. Keep the oven door closed during the first 30 minutes of baking - this is very important else you may cause the eclairs to sink. When they are fully bake they will be golden and hollow-sounding when tapped.

Transfer to a wire rack and pierce the end of each with a cocktail stick, to allow any steam to escape. Leave to cool fully.

Place the dark chocolate and 100ml cream in a microwave-safe bowl. Microwave for about 1 minute, until the cream is hot but not boiling, then leave to sit for 3 minutes to allow the chocolate to melt.

Stir with a fork until you have a glossy, smooth chocolate ganache. If you still have lumps of chocolate, microwave in additional bursts of 15 seconds until melted and smooth. Set aside.

Now to fill the eclairs with cream or creme patissiere. Start by using a long skewer to make space inside the eclairs - insert it in the cocktail stick hole and gently wiggle it around to create an internal space for the filling.

Take a piping bag with a cupcake filler nozzle (this makes filling so easy, if you don't have one you can slice the eclairs in half, pipe and sandwich the filling). Fill the bag with the creme patissiere - don't stir the set creme pat, just spoon it into the bag, then insert the filler nozzle into the end of an eclair and squeeze gently to fill. If you are using cream, add the vanilla and whisk until it has the consistency of thick custard, then pipe.

Once you have filled the eclairs, carefully dip the top half of each into the chocolate ganache, until you have a beautiful batch of eclairs.