In a medium saucepan, bring water and butter to a boil. Stir in flour and salt all at once. Cook and stir for about 1-2 minutes, or until the mixture pulls away from the sides and forms a ball.

Transfer the dough to a mixing bowl and let it cool for about 5 minutes.

Add eggs one at a time, mixing well after each addition until the dough is smooth and glossy.

Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper. Pipe 4-inch long strips of dough onto the parchment.

Bake for 20-25 minutes or until golden brown.

In a medium saucepan, whisk together milk, sugar, cornstarch, and coffee powder over medium heat until it comes to a gentle simmer.

In a separate bowl, whisk egg yolks and slowly pour about half of the hot mixture into the egg yolks, whisking constantly.

Return the mixture to the saucepan and cook, stirring continuously until it thickens. Remove from heat and stir in vanilla extract and butter.

Pour the pastry cream into a bowl and cover with plastic wrap touching the surface. Chill for about 2 hours until set.

Once éclairs are cooled, use a sharp knife to make a small slit in the side of each pastry.

Fill a piping bag with the cooled pastry cream and pipe it into the éclairs.

In a separate bowl, whip the heavy cream and powdered sugar until soft peaks form.

Use this cream to pipe on top of your filled éclairs. Dust with cocoa powder before serving.

Serve the éclairs at room temperature and enjoy them at cozy gatherings or impress friends at brunch!