Preheat Oven:

• Preheat your oven to 375°F (190°C).
• Line a baking sheet with parchment paper.

Prepare the Dough:

• In a saucepan over medium heat, combine water, butter, sugar, and salt.
• Bring to a boil, then remove from heat.

Incorporate Flour:

• Add the flour all at once, stirring vigorously with a wooden spoon.
• Return to heat and cook for 1-2 minutes, stirring continuously, until the dough forms a ball and pulls away from the pan.

Add Eggs One by One:

• Transfer the dough to a mixing bowl and let it cool for 5 minutes.
• Add eggs one at a time, beating well after each addition until smooth and glossy.
• Stir in vanilla extract.

Pipe and Bake:

• Transfer the dough to a piping bag fitted with a large round tip.
• Pipe 4-inch long strips onto the baking sheet, spacing them 2 inches apart.
• Bake for 30-35 minutes, or until golden brown and puffed.
• Turn off the oven, crack the door open, and let them cool inside for 10 minutes to prevent collapse.

Heat the Milk:

• In a saucepan, heat milk over medium heat until steaming (but not boiling).

Whisk Egg Yolks and Sugar:

• In a separate bowl, whisk egg yolks, sugar, and cornstarch until smooth and pale.

Temper the Eggs:

• Slowly pour half of the hot milk into the egg mixture, whisking constantly.
• Pour the mixture back into the saucepan.

Thicken the Cream:

• Cook over medium heat, whisking constantly, until thickened (2-3 minutes).
• Remove from heat, stir in butter and vanilla extract.

Cool and Store:

• Transfer to a bowl, cover with plastic wrap touching the surface, and chill for 1 hour.

Heat the Cream:

• In a small saucepan, heat heavy cream until just simmering.

Melt the Chocolate:

• Pour the hot cream over chopped chocolate, let sit for 1 minute, then stir until smooth.
• Stir in butter and corn syrup for extra shine.

Fill the Éclairs:

• Once the choux pastries are completely cool, poke 2-3 small holes on the bottom.
• Fill a piping bag with the chilled pastry cream and pipe it into each éclair.

Dip in Chocolate Glaze:

• Dip the top of each éclair into the warm chocolate glaze, letting the excess drip off.

Let Set and Serve:

• Place on a wire rack and allow the glaze to set for 10-15 minutes before serving.