Make the Choux Pastry:
- Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper.
- In a medium saucepan, bring the water, butter, sugar, and salt to a rolling boil over medium heat.
- Add the flour all at once, reduce the heat to medium-low, and stir vigorously with a wooden spoon until the mixture forms a smooth dough that pulls away from the sides of the pan, about 1-2 minutes.
- Transfer the dough to a mixing bowl and let it cool for a few minutes. Beat in the eggs, one at a time, fully incorporating each egg before adding the next, until the dough is smooth and shiny.
- Transfer the dough to a piping bag fitted with a large plain tip. Pipe the dough onto the prepared baking sheet in 4-inch long and 1-inch wide strips.
- Bake for 15 minutes, then reduce the oven temperature to 375°F (190°C) and bake for another 25-30 minutes, until the éclairs are golden brown and hollow sounding when tapped. Remove from the oven and let cool on a wire rack.
Prepare the Pastry Cream:
- In a medium saucepan, heat the milk and half the sugar over medium heat until it just begins to simmer.
- In a bowl, whisk together the egg yolks, the remaining sugar, and cornstarch until smooth.
- Gradually whisk in about half of the hot milk into the egg mixture to temper the eggs. Then, pour the egg mixture back into the saucepan with the remaining milk.
- Cook over medium heat, whisking constantly, until the mixture thickens and comes to a boil. Remove from heat and stir in the vanilla extract.
- Transfer the cream to a bowl and cover with plastic wrap, pressing it directly onto the surface to prevent a skin from forming. Chill in the refrigerator until cold.
Make the Chocolate Glaze:
- Place the chopped chocolate in a bowl. In a small saucepan, heat the heavy cream and butter until it just begins to simmer.
- Pour the hot cream over the chocolate and let it sit for a few minutes. Then, stir until smooth and glossy.
Assemble the Éclairs:
- Once the éclairs have cooled, use a small knife to make a hole at each end of the underside of the éclair.
- Fill a piping bag fitted with a small nozzle with the chilled pastry cream. Pipe the cream into the éclairs through the holes until filled.
- Dip the top of each filled éclair into the chocolate glaze, letting any excess drip off.
Allow the Chocolate Éclairs to set for a few minutes before serving. These exquisite pastries are best enjoyed fresh, offering a delightful combination of creamy, chocolaty, and puffy textures. Whether for a special occasion or a luxurious treat, homemade Chocolate Éclairs are sure to delight any dessert lover.