Soften the unsalted butter at room temperature. Combine all the craquelin ingredients in a mixing bowl and mix until they come together into a dough.
Place the dough on a sheet of parchment paper and cover it with another sheet. Roll it out to about 20 cm × 14 cm and 2–3 mm thick, keeping the thickness as even as possible. Freeze for 15 minutes.
Once firm, cut out 6 discs with a round cutter and return them to the freezer until needed.
Preheat the oven to 180°C (355°F) with the rack in the middle. Line a baking tray with a perforated silicone mat. Dip the round cutter lightly in flour and stamp circles on the mat as piping guides. Fit a piping bag with the round tip and set aside.
In a small saucepan, combine the water, whole milk, sugar, salt, and unsalted butter. Heat over medium-low until the butter has melted completely and the liquid comes to a boil.
Remove from the heat, add the pastry flour, and stir with a silicone spatula until no dry flour remains.
Return the pan to medium-low heat. Keep cutting through and turning the dough with the spatula for about 3 minutes, until the surface looks slightly glossy and you hear a faint sizzling from the bottom of the pan.
Transfer the dough to a mixing bowl. While it is still hot, pour in about half of the beaten eggs and combine using a cutting-and-folding motion. Once incorporated, keep adding the egg in batches, each time about half of what remains, mixing well after each addition. Stop when the paste is stretchy and can be pulled into long strands with the spatula. When you lift the spatula, the paste should fall back into the bowl under its own weight and leave a thin, elongated inverted triangle on the spatula, with smooth edges and sides that curve slightly inward near the tip.
Fill the prepared piping bag with the paste. Holding the tip slightly above the tray, pipe the paste onto the guides. Mist the piped paste with water from four directions using a spray bottle. Take the craquelin discs out of the freezer and gently lay one on top of each mound. Place in the preheated oven, lower the temperature to 170°C (340°F), and bake for 45 minutes, then reduce to 110°C (230°F) and bake for another 45 minutes.
In a mixing bowl, whisk the egg yolks with the granulated sugar until the sugar has mostly dissolved. Whisk in the vanilla paste, then the pastry flour and corn starch. Add the whole milk in three additions, whisking until smooth after each.
Strain into a small saucepan. Cook over medium-low heat, stirring constantly, until the mixture comes to a boil. Remove from the heat and stir in the unsalted butter while still hot.
Transfer to a container, press plastic wrap directly onto the surface, and refrigerate until completely cold.
Whip the whipping cream at medium speed until it just stops flowing. Take the chilled custard out of the fridge and stir it with a spatula until smooth. Add the whipped cream and fold until combined.
Once the puffs have cooled completely, slice off the tops with a serrated knife. Fill a piping bag with the custard cream, pipe it generously into each puff, replace the top, and dust lightly with icing sugar.
This recipe uses a 5.5 cm round cutter and a 1.1 cm round piping tip. The eggs are North American large eggs, about 60 g each in the shell.
Keep the beaten eggs warm before using them. Eggs straight from the fridge can be soaked in 60°C water for 15–20 minutes to bring them up to temperature.
Yellow sugar sits between brown sugar and white sugar in flavour and aroma. Granulated sugar works as a substitute.
Do not roll the craquelin too thick, or it will weigh down the paste and limit how much the puffs rise.
Compared with parchment paper, a silicone mat keeps the bottoms of the puffs flatter, and a perforated mat conducts heat better than a plain one.
Sifting the pastry flour beforehand reduces lumps and makes the paste easier to mix smoothly.
While cooking the dough, keep pressing and turning it with the spatula so it heats evenly inside and out. In a non-stick pan you will not see the thin film that forms on the bottom of a regular pan, so time it for roughly 3 minutes and go by the surface of the dough and the sound from the pan.
After several additions of egg, the paste changes quickly. Mix well and check after every addition. A slightly stiff paste is fine, but a paste that is too loose will not rise properly.
Hold the piping tip a little above the tray so the piped mounds are tall, which helps the puffs rise higher. Do not press the craquelin down, just lay it on gently so you do not flatten the mound.
YouTube