For the cream puff shells:
Place oven rack one place below middle. Preheat oven to 400F degrees. Set aside a regular muffin pan (12 or more), lightly buttered (Cooking spray or neutral oil brushed with a pastry brush also works). Note: If using a dark non-stick pan, preheat oven to 375F degrees (see notes for more information).
In a medium sauce pan, bring water and butter to a low boil over medium-high heat. Reduce heat to medium-low and add flour, stirring well until mixture forms a ball. Remove from heat. Stir in eggs, one at a time, beating with wooden spoon or large fork until dough is smooth. Beat additional 10 to 15 seconds as this will increase the volume of the dough.
Using a tablespoon, drop dough into deep muffin tins. This doesn't have to be an exact measurement, but depending on how big you want your pastry to be. Divide all the batter between 12 muffins.
Bake pastries for 25 to 35 minutes or until puffed and golden brown. (Might take longer in the non-stick pan at the lower temperature). Important that the puffs are golden/crisp or they may collapse. Even when they look done, I leave them in a full minute or so longer. Turn oven off and open the oven door. Pull oven rack out about half way and let shells sit for approximately 20 minutes. Remove from oven and cool completely in the muffin tin before removing to wire racks. If your shells stick a bit to the tins, gently use a fork or butter knife to pull them away from the sides of the pan.
(The pastry shells can be prepared the day before. Just lightly cover with foil when completely cooled and let sit at room temperature.)
Cook's note: Ingrid baked the pastries on a baking sheet about three inches apart, but my smart aunt decided the muffin tins make a nice shape to hold the cream. Either method works, but Ingrid's way will produce a little flatter shaped shell. If you prefer to make them on the baking sheet, be sure to line it with parchment paper before spooning or piping the choux pastry dough from a pastry bag.
For the custard pastry cream filling:
Place the 4 egg yolks in a medium bowl. Whisk them together and set aside.
Mix sugar, flour and salt in a medium saucepan. Stir in warm milk. Cook over medium heat, stirring frequently. Mixture will thicken and bubble. Once it starts to bubble, cook one minute more while still stirring.
Remove from heat. Quickly whisk about half of the mixture into beaten egg yolks.
Blend this back into remaining hot mixture in the saucepan. Whisk constantly until mixture starts to bubble again. Cook for another 30 seconds or so but do not stop whisking.
Remove from heat and add vanilla- Don't forget the vanilla and use good quality vanilla since this flavor is the base of the entire filling.) Set aside, cover with plastic wrap and let cool completely. You can set the custard in the refrigerator to cool quickly. The custard will continue to thicken as it cools.
For the sweetened whipped cream:
Whip your cream using electric beaters or stand mixer and add sugar and vanilla to your liking.
Assembling the cream puffs:
Cut off pastry shell tops and scoop out the insides of top and bottom to make room for the custard and whipped cream. The insides might be moist. Just pull that all out being careful not to make a hole go through the bottom.
Pour about one cup powdered sugar into a bowl to dip the cream puffs in.
Dip the bottom of the puff into powdered sugar, then repeat with top of puff. This will coat the puffs and gives a "French pastry" decadent look to the finished cream puff.
Fill bottom of puff with Custard Cream Filling. Top generously with sweetened whipped cream.
Replace top of puff. The top won't cover entirely but sits like a decorative hat. Place puffs in refrigerator, uncovered, chilling for 4 hours. Do not cover the puffs in fridge or you run the risk of the powdered sugar evaporating. Puffs can remain in the refrigerator overnight this way.
More notes for preparing ahead of time:
You may completely assemble cream puffs the night before serving, they actually get better over time. Cover loosely with foil.
For transporting, place completed cream puffs back into muffin tins, cover lightly with foil and they're ready to go!
Makes 12 cream puffs if made in muffin tin.