Start by preheating your oven to 375 degrees Fahrenheit.
Take a medium-sized saucepan and add your water, sugar, salt, and butter. Heat up all these ingredients until the butter melts and the mixture starts simmering.
Remove the pan from the heat and pour in the flour. Make sure to stir continuously before replacing the pan on the heat. Continue to stir for approximately 1 minute.
Allow 5 minutes for the contents of the pan to cool down before adding the eggs. Only add a single egg at a time, and stir thoroughly after adding each egg.
By this point, you should have a thick batter with a glossy consistency.
Transfer the batter to a pastry bag and pipe rounds measuring 1 inch and 2 inches onto some baking parchment.
Place the rounds in the preheated oven for about 25 minutes (up to 30 minutes if necessary). When the pastry is fully cooked, you should have some adorable-looking choux.
To start the process of making the pastry cream, pour your milk into a saucepan and add the vanilla bean. Turn the heat to a low-medium setting and allow the milk to heat up while the flavor of the vanilla bean infuses through the milk.
Meanwhile, take a large bowl and whisk the yolks, egg, and sugar into the flour so that the ingredients combine fully.
By now, your milk should be simmering. Take it off the heat and pour a splash of the milk into the bowl, stirring thoroughly, before adding the rest of the bowl’s contents to the pan.
Continue to stir all the ingredients together consistently over the heat so that it doesn’t catch and burn. Within 3 minutes, you should notice that the mixture is thicker. This is your sign to remove the pan from the heat and let everything cool down.
Once the pastry cream mixture has cooled, you can mix one cup of the cream with your jam.
Next, combine the milk and sugar for the glaze by stirring. If you want, you can also add any color of food coloring.
Using a piping bag, pipe your pastry cream into one of the larger rounds of baked pastry. Keep adding the cream until the bottom pastry is full.
Now take a smaller round of pastry and pipe the plum-flavored cream into it.
Go back to the bigger of the two choux and dip it gently into your glaze first, followed by the smaller choux.
Carefully stack the smaller choux on top of the larger one. Repeat until you have used up all of your choux and pastry cream.