Preheat the oven to 425 degrees.
Line a sheet pan with parchment paper.
In a large saucepan, bring the water, butter, salt and sugar to a rolling boil over medium-high heat. When it boils, immediately take the pan off the heat.
Stirring with a wooden spoon, add all the flour at once and stir hard until all the flour is incorporated, 30 to 60 seconds.
Return to the heat and cook, stirring about 30 seconds.
Scrape the mixture into a mixer fitted with a paddle attachment (or use a hand mixer).
With the mixer running at medium speed, add 3 eggs, 1 egg at a time.
Stop mixing after each addition to scrape down the sides of the bowl.
Mix until the dough is smooth and glossy and the eggs are completely incorporated.
The dough should be thick, but should fall slowly and steadily from the beaters when you lift them out of the bowl.
If the dough is still clinging to the beaters, add the remaining 1 egg and mix until incorporated.
Pipe the choux into circles and then brush with the egg wash.
Bake at 425F for 15 minutes then reduce heat to 375F for 20-25 min or until golden brown.
Fill the cooled donuts with pastry cream, you might want to cut small holes in the bottom for easy piping.
Dip in chocolate ganache and decorate.