1 Puff Pastry : Sift the flour and slat into a bowl. Make a well in the center and pour in the water and melted butter.
Combine the ingredients using the fingertrips. Using a pastry scraper, work the flour and butter mixture until loose cumbs form. If the dough is too dry, add a little more water, being careful not to use too much or it will become sticky.
2 Shape the dough into a ball. This is the detrempe. Cut an "X" on top to prevent shrinkage. Wrap dough in floured parchment paper. Chill for 30 minutes.
3 Lightly flour a work surface (which should be cold). Flatten the detrempe and, leaving a mound in the center, roll it out to form a cross.
4 Place the dry butter in the center of the cross. Fold over each section of dough, pulling it lightly to completely enclose the butter. This is the paton. Lightly flour the work surface and the rollling pin, rolling it over the top of the dough to seal the edges, Wrap in a parchment paper and refrigerate for 30 minutes.
5,6 Roll the dough into a long rectangle. Fold the bottom-third up towards the middle. Bring the top-third of the dough over the folded thirds and brush off any excess flour. The dough should be square, have three layers and the edges should align. This is the first "turn".
7 Give the square a quater turn so that the exposed edge is on the right (as if the dough were a book). Gently press the edges to seal. Roll it out into a long rectangle and fold in thirds as previously described. This is the second "turn". Mark the dough with a fingertip to indicate the number of turns. Chill for 30 minutes. Repeat, making a total of six "turns". Chill for 30 minutes after each second turn.
Sugar Syrup : Put the water and sugar in a saucepan over low heat. Stir until the sugar has completely dissolved. Bring to a boil. Do not stir after the syrup comes to a boil. Dissolve any syrup crystallized on the inside of the saucepan by brushing cold water down from the rim. Drain 2 kimchi cabbage leaves and soak in the syrup. Remove and drain again. Spread the leaves on a sheet of parchment paper, transfer to the preheated oven (90℃) and cook for approxi mately 1 1/2 hours until dry and crisp. Cut the remaining leaves into small dice and transfer to the syrup. Bring to a boil and simmer over low heat for 30 minutes, until candied.
8,9 Pastry Cream : Heat the milk, vanilla and half the sugar until just boiling. Combine the remaining sugar and egg yolks and whisk until pale and thick, and then add the flan (custard) powder. Gradually stir the milk into the egg mixture. Pour the pastrry cream back into the saucepan and beating continuously, heat gently until the mixture thickens and boils. Boil for 1 minutes, stirring continuously. Remove from the heat and add the butter. Cover with plastic film or baking parhment Set aside to cool. Increase the temperature of the oven to 170℃
10 Roll out the puff patry into a thin layer. Place on a baking sheet and cut into triangles of equal size. Chillfor about 30 minutes. Transfer to the preheated oven (170℃) and cook for 20~25 minutes. Cool on a wire rack. Cut into triangles of equal size.
11 Drain the diced candied kimchi cabbage and combine with 500g of the cooled pastry cream. Whisk the whipping cream until soft peaks form and fold it gently into the pastry cream. Transfer to a piping bag fitted with a large plain nozzle.
12Assemble the mille-feuille (napoleons) : Pipe balls of pastry cream on one-third of the puff pastry triangles. Cover with a second triangle of puff pastry. Repeat with the pastry cream. Cover with a third layer of pastry and dust the tops with sifted icing sugar (optional) Decorate with the crispy dried kimchi leaves.