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.

Incorporate the eggs

• Transfer the dough to a mixing 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

• Preheat the oven to 190 °C.
• Pipe the dough into even éclair shapes on a lined baking tray.
• Bake until puffed and golden, without opening the oven during baking.

Cook the pastry cream

• Heat the milk in a saucepan.
• Whisk the egg yolks with the sugar and cornstarch in a bowl.
• Pour the hot milk over the yolks, return everything to the pan and cook, whisking, until thick; stir in the vanilla and let cool.

Make the chocolate glaze

• Melt the dark chocolate with the heavy cream over low heat or in a bain-marie.
• Stir until smooth and glossy.

Fill and glaze the éclairs

• Poke small holes in the base of each cooled éclair.
• Fill with the pastry cream using a piping bag.
• Dip the tops in the chocolate glaze and let set on a cooling rack.