Preheat your oven to 190˚C (350˚F) and line two baking trays with parchment paper.
In a medium saucepan combine water, milk and butter with sugar and salt, then bring to a boil, making sure the butter has melted. After the mixture has reached the boiling point, remove the saucepan from the heat and add the flour, mixing quickly with a wooden spoon to combine and form a thick paste.
Return to heat and stirring constantly, cook for a couple of minutes to dry it. When it's done, it should clump into a ball and there will be a thin film on the bottom.
Transfer the dough to the bowl of a standing mixer fitted with a paddle attachment and mix on medium speed to cool it down before adding the eggs.
In a small bowl mix the eggs (230 g) using a whisk and then slowly pour it into the cooled dough in batches. Make sure all of it is thoroughly incorporated. At this point, you need to test the consistency of the batter. Dip the paddle attachment and pull it up. If the batter forms a loose "V" shape, then your choux pastry is done. If it's too stiff, beat another egg and add it to the batter. For more information on this, check the post above.
Once your choux pastry is ready, put it in a large piping bag fitted with a round nozzle. I use Wilton 2A. Keeping your piping bag vertically, pipe blobs approx. 3 cm in diameter. Leave room between each blob, because they will rise quite a lot once baked.
Remove the craquelin from the freezer and using a round cookie cutter, cut rounds the size of the piped choux pastry. Place on top of each mound of pastry. Since you have two trays, place the craquelin on the other tray just before baking.
Bake in a preheated oven for approx. 35 minutes. Don't open the oven door, because cream puffs could collapse. They're done when they're golden brown. Poke each one with a chopstick to help steam escape and place them on a cooling rack to cool completely.
for the craquelin
Place all the ingredients in a stand mixer fitted with the paddle attachment. Beat on medium-hight speed until combined. Turn out the sticky dough on to a large piece of parchment paper then top with another piece. Using a rolling pin, roll out the dough 2-3 mm thick. Place the dough, still between the parchment sheets, in the freezer for an hour or until you are ready to use it.
for the pistachio paste/butter
In a small, sharp food processor mix shelled, salted and roasted pistachios for approx. 15 minute until it transforms into a butter/paste. If it seems like it's not coming together, add a teaspoon or two of vegetable oil to help it combine into a smooth paste. DO NOT ADD WATER.
for the pistachio crème mousseline
In a medium sized saucepan, heat the milk just until boiling point. In the meantime, in a separate bowl, combine the egg yolks, egg, cornstarch, sugar and salt using a whisk.
Once the milk has reached scalding point, start pouring it SLOWLY to egg mixture, whisking continuously, so you don’t cook the eggs. About half to ⅔ of hot milk will do. Once you tempered the egg mixture, add it to the pot with remaining milk and continue cooking, whisking constantly, until it thickens.
Once it’s done, stir in vanilla extract and whisk until everything is combined. Strain the pastry cream to a clean bowl through a sieve, to get rid of any cooked egg bits and lumps. Cover with cling film touching the surface to prevent skin forming. Leave it to cool on room temperature, or put it in the fridge to speed up the process. Just make sure it's room temperature prior to using.
In a bowl of a stand mixer fitted with the paddle attachment, beat the butter until pale and fluffy (approx. 5 minutes). Then add spoonful by spoonful of previously made pastry cream. Mix until it's all nicely incorporated and with no lumps. Add pistachio paste and mix until everything is combined.
for raspberry jam
Cook frozen raspberries with sugar over a medium-high heat until it reaches boiling. Turn the heat down and let it simmer for approx. 15 minutes or until it thickens. It’s better to be thicker than looser, the plan is to lose a lot of water content and have concentrated flavour. Strain the jam through a sieve to get rid of raspberry seeds and make it smooth and beautiful. Cover it with cling film and leave it to cool in the fridge.
Using a sharp serrated knife, cut the tops of the cream puffs, approx. ¾ of the way up. Place pistachio creme mousseline into a piping bag fitted with preferred nozzle (Wilton 1A or 6B). On the bottom of each cream puff put 1-2 teaspoons of raspberry jam then top it with pistachio creme mousseline. Cover with cream puff tops and sprinkle with powdered sugar.
They're the best eaten the same day. Keep them in the fridge before serving.