1.  Preheat the oven to 400°F (200°C) and line a baking tray with parchment paper. 
2.  Combine water, butter, and salt in a saucepan and bring to a boil. 
3.  Add the flour all at once and stir vigorously until a smooth dough forms. 
4.  Cook for 1–2 minutes, stirring constantly, until the dough pulls away from the pan. 
5.  Transfer the dough to a bowl and let it cool slightly. 
6.  Add the eggs one at a time, mixing well after each addition. 
7.  Transfer the dough to a piping bag. 
8.  Pipe long strips onto the prepared baking tray. 
9.  Bake for 25–30 minutes, until puffed and golden. 
10.  Turn off the oven and leave the éclairs inside for 5 minutes with the door slightly open. 
11.  Remove and cool completely. 

Make the Caramel Cream

1.  Heat the milk until steaming. 
2.  Whisk the egg yolks, sugar, and cornstarch until smooth. 
3.  Slowly whisk the hot milk into the egg mixture. 
4.  Return the mixture to the saucepan and cook over medium heat, stirring constantly, until thick. 
5.  Stir in the caramel sauce and vanilla. 
6.  Cover and refrigerate until completely chilled. 

Fill and Glaze

1.  Make small holes underneath each éclair. 
2.  Pipe the chilled caramel pastry cream into the shells. 
3.  Mix powdered sugar, caramel sauce, and milk until smooth. 
4.  Dip the tops of the éclairs into the caramel glaze. 
5.  Refrigerate for 15–20 minutes to set. 
6.  Serve chilled or slightly cool.