Deliciously crisp, puffy and perfect chocolate eclairs 

For the Choux Pastry:

1. Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper.
2. In a saucepan, combine water and butter over medium heat. Bring to a boil.
3. Add flour and salt all at once, stirring vigorously with a wooden spoon until the mixture forms a ball. Remove from heat.
4. Let the dough cool for a couple of minutes. Add the eggs, one at a time, beating well after each addition, until the dough is smooth.
5. Transfer the choux pastry to a pastry bag fitted with a large round tip. Pipe 4-inch long strips onto the prepared baking sheet.
6. Bake for 15 minutes at 425°F, then reduce the oven temperature to 375°F (190°C) and bake for an additional 15-20 minutes or until the eclairs are golden brown and puffy.
7. Remove from the oven and let them cool on a wire rack.

For the Pastry Cream Filling:

1. In a saucepan, heat the milk until just below boiling.
2. In a bowl, whisk together sugar, cornstarch, and egg yolks until smooth.
3. Gradually whisk the hot milk into the egg mixture.
4. Return the mixture to the saucepan and cook over medium heat, stirring constantly, until it thickens.
5. Remove from heat, stir in the vanilla extract, and let it cool.

For the Chocolate Ganache:

1. In a small saucepan, heat the heavy cream until it just starts to boil.
2. Pour the hot cream over the chocolate chips and let it sit for a minute. Stir until smooth.
3. Add butter and stir until glossy.

Assembling the Eclairs:

1. Cut the cooled eclairs in half horizontally.
2. Spoon or pipe the pastry cream into the bottom half of each eclair.
3. Dip the top half of each eclair into the chocolate ganache.
4. Place the chocolate-dipped tops back onto the cream-filled bottoms.
5. Allow the chocolate eclairs to set in the refrigerator for at least 30 minutes before serving.

Enjoy these deliciously crisp, puffy, and perfect chocolate eclairs with a rich and creamy pastry cream filling!