Make the choux pastry

• Bring the water, butter, salt and sugar to a boil in a saucepan.
• Remove from the heat, add the flour at once and stir vigorously until a smooth dough forms.
• Return to low heat and dry the dough, stirring, until it pulls away from the pan.

Beat in the eggs

• Transfer the dough to a bowl and let it cool slightly.
• Add the beaten eggs gradually, mixing until the dough is smooth, glossy and forms a soft ribbon.

Pipe and bake the éclairs

• Preheat the oven to 190 °C and line a baking tray.
• Pipe the dough into éclair shapes on the tray.
• Bake until puffed, golden and firm.

Cook the vanilla pastry cream

• Heat the milk with the vanilla seeds in a saucepan.
• Whisk the egg yolks, caster sugar and cornstarch in a bowl.
• Pour the hot milk over the yolks, whisking, then return everything to the pan and cook, stirring, until thick.

Chill the cream

• Pour the pastry cream into a dish, cover with film in contact and refrigerate until cold.

Fill the éclairs

• Poke small holes in the base of each cooled éclair.
• Fill a piping bag with the vanilla cream and pipe it into the éclairs.

Glaze with chocolate

• Melt the dark chocolate with the heavy cream until smooth.
• Dip the top of each éclair into the glaze and let it set on a cooling rack.