Check out the body of this post if you have any questions as it is very full of more in-depth information. You can also check out this Choux Pastry Guide if you are a beginner choux maker and have questions.
Want to skip out on making the diplomat cream and instead just fill it with whipped cream? Totally up to you! Or you could fill it with a stabilized sweetened whipped cream.
You can make the choux pastry directly in the pot you cooked the flour in, however it will take a bit longer to cool than if you transferred it to another bowl. I choose to make it directly in the pot because that means one less bowl to dirty! However, don’t do this if your pan has formed a very thick film on the bottom. Instead, transfer it to a bowl. Alternatively, if you didn’t want to make this by hand, you could mix the eggs in an electric mixer. They both work the same, in terms of needing to make sure to fully incorporate the egg into the mixture before adding more and making sure to not add too much egg that the mixture is runny.
Piping tips: Hold the piping bag directly vertical with the tray. Gently apply even pressure to the piping bag until the choux pastry hits the sheet tray. Just slightly, pull the bag up as the choux comes out, so it forms a mound about 1” up. Once done, stop the pressure and gently flick your wrist in a circle around the mound, to prevent a peak from forming. If a peak does form, no worries. Use a wet finger to gently push it down. This prevents the peaks from burning in the oven.