Preheat the oven to 400 degrees F. Line a baking sheet with parchment paper and set aside. In a medium saucepan combine water, butter and salt and bring to a rolling boil. Add the flour all at once, stirring vigorously. Cook and stir over medium high heat until mixture forms a ball. Remove from heat. Set aside and cool for 10 minutes.
Add eggs, one at a time, beating well with a wooden spoon after each addition, until the dough is smooth.
Transfer the dough by heaping tablespoons onto prepared baking sheet. Bake for 35 minutes or until golden brown and firm. Transfer cream puffs to a wire rack and let cool completely.
To make the Vanilla Pastry Cream
In a medium sized heavy bottom saucepan combine sugar and cornstarch. Whisk in the milk. Cook and stir over medium heat until thickened and bubbly. Cook and stir for 2 minutes more. Remove the pan from the heat.
In a mixing bowl, whisk the egg yolks until smooth. Gradually whisk in 1 cup of the milk mixture. Add the egg mixture to the remaining milk mixture in saucepan. Bring to a gentle boil. Reduce heat. Cook and stir for 2 minutes more.
Remove the pan from heat. Stir in the butter and vanilla extract.
Pour pudding into a bowl. Cover surface of pudding with plastic wrap. Chill.
Notes
Choux Pastry tips
Making a choux dough is not hard. However, you do need to follow the directions as written or you could end up with a cream puff shell that doesn't puff up. Below are some tips on making the best most puffed up cream puff shell.
Allow the choux dough to cool 10 minutes before adding the eggs. Adding it sooner can cause the eggs to scramble from the heat of the dough.
Beat the eggs into the choux dough one at a time until completely incorporated.
Make sure the oven temperature is accurate. A hot oven is needed to make the shells puff
Once the cream puff shells have finished baking, turn the heat off but leave the shells in the oven. This will help them to dry out more and be firmer.
Make sure the cream puff shell has completely cooled before filling with the pastry cream.
Vanilla Pastry Cream tips and substitutions
Vanilla Pastry Cream should be thick. It is similar to pudding, only thicker and holds up on its own better. Pastry cream is often used in pie recipes as it can be sliced into and hold it's shape.
Temper the egg yolks by quickly whisking 1 cup of the hot cream filling into the egg yolks. Once the egg yolks and pastry cream are creamy and smooth, whisk it into the remainder of the hot filling.
Flour can be substituted for cornstarch. However, when substituting flour, it needs to be doubled. In this instance you would need ⅔ cup of flour. I highly recommend sticking to cornstarch for the thickening agent.
Save the egg whites for future use. They can be frozen for future use so they don't spoil. I like to make these Cinnamon Roasted Nuts whenever I have some extra egg whites hanging around.