For the pastry, preheat oven to 425°F. Line 2 baking sheets with parchment paper and set aside.

In a medium saucepan bring the water, butter, salt and sugar to a rapid simmer. Remove from heat and immediately stir in the flour with a wooden spoon. Keep stirring rapidly until the mixture comes together for about 30 to 60 seconds. Return to the heat and cook, constantly stirring rapidly, for about 30 seconds. Transfer the mixture to a stand mixer, fitted with the paddle attachment, and stir on medium. Slowly add the eggs, one at a time, mixing well after each addition. Scrape down the sides and bottom of the bowl and mix once more. The batter should be thick, but fall slowly away from the paddle. Transfer to a large pastry bag fitted with a plain circle tip.

Pipe out the eclairs onto the prepared baking pans, to about 2 inch think logs. Make sure to leave about 2 inches of space apart. Brush the surface of each eclair with the egg wash and bake for 15 minutes. Reduce the heat to 375°F and continue to bake until puffed and golden brown, about 25 minutes more. Let the eclairs cool completely on the baking sheets before filling.

For the pastry cream, in a small saucepan bring the milk to a simmer. Combine the egg yolks, sugar and cornstarch in a large pot. Whisk until completely combined. Slowly whisk in the heated milk into the egg yolk mixture. Once all the milk has been added, place the pot over medium-high heat. Cook, stirring constantly until the mixture has bubbled and thickened. Remove from heat and stir in the butter and vanilla extract. Transfer to a small bowl and allow to cool. Chill for 1 hour in the fridge.

For the glaze, whisk together the powdered sugar, vanilla and enough milk as needed to create a pourable glaze.

Fill the eclairs with the pastry cream, using a piping bag, then tip each into the glaze and top with sprinkles. Allow to set and serve immediately. Enjoy!