Pre-heat the oven to 230 degrees celsius.
In a good-quality saucepan, add the milk, water, butter, sugar, and salt and bring it to a boil on medium heat. Make sure the butter is completely melted.
100 ml full-fat milk, 100 ml water, 90 grams unsalted butter, 2 grams sugar, 2 grams salt
Once the mixture starts boiling, remove from the heat, add the flour, and immediately start mixing with a wooden spoon or silicon spatula so that the flour does not form any lumps in the dough. Continue mixing until you have a smooth, thick dough. This mixture is called the panade.
110 grams all-purpose flour
Continue mixing the panade until almost all the steam has been released, then add the beaten eggs, one at a time, mixing after each addition. Keep mixing until all the eggs have been incorporated and you have a smooth, thick, and shiny dough. The dough should not be too thick or thin and should not fall off like a ribbon from the spoon but be able to hold a little bit shape.
200 grams beaten eggs
Transfer the prepared dough into a piping bag without a tip and cut a 1-1.5 cm opening at the end. Line a baking tray with baking paper and use a 4 cm cookie cutter or bottle cap to create circles across the paper to act as a guiding template so that the buns are sized evenly. Flip the paper before piping the dough.
To pipe the dough, place the piping bag in the center of a circle at an angle, and pipe the dough in one single motion without moving the piping bag. This will form a thick blob of dough, which is exactly what you want. Make sure not to pipe too much or too little, and leave enough space between each one to give them space to rise.
Cover each dough blob with egg wash gently.
20 grams extra egg for egg wash
Cut the craquelin in the same size as the choux buns, using the same cookie cutter or bottle top, and place each one gently on each dough blob. using an offset spatula. The craquelin softens very fast so work quickly and if it becomes too soft, place it in the fridge for another 10 minutes.
Before placing the baking tray into the oven, reduce the temperature to 170 degrees celsius. Bake the buns for 20 minutes undisturbed, without opening the oven at all as any drop in temperature will deflate the buns.
After 20 minutes, open the oven door slightly for 5 seconds to release the steam and bake for another 15-20 minutes until golden brown.
Once the buns have completely cooled down, push the whipped cream piping bag into the bottom center of the bun and fill it halfway through, then fill the remaining bun with the mango curd through the same hole until the buns are full. Don't overfill them as they may explode. Clean any excess from the bottom with an offset spatula or knife.
Top each bun with a little swirl of whipped cream and serve fresh.