Napoleon Cake (Mille-Feuille)

👨‍🍳 Method

For the Wrapping Dough

1. 1
   Thaw the puff pastry in the fridge overnight, until pliable but still cold.

   Refrigerator

   💡Work with store-bought dough while it's cold: warm puff pastry gets sticky and won't puff in the oven, and phyllo sheets dry out fast, so keep the waiting sheets covered with a damp towel.

For the Cream Filling

1. 2
   Heat the milk to just below a boil.

   StovePot
2. 3
   In a bowl, whisk the egg yolks, sugar and flour.

   BowlWhisk
3. 4
   Pour the hot milk in a thin stream into the mixture, whisking constantly.

   ⚙ Tempering eggsWhisk

   💡The hot liquid goes into the eggs slowly while whisking, and only about a third of it in the first batch: that way they warm gradually and don't turn into scrambled eggs.
4. 5
   Return to the pot and cook over medium heat, stirring constantly, until the cream thickens and bubbles in the center, then cook 1–2 more minutes.

   StovePot

   💡Stir nonstop until it bubbles: only then does the starch thicken fully, and the cream won't turn runny later.
5. 6
   Add the vanilla and stir.
6. 7
   Transfer to a bowl, cover with plastic wrap touching the surface of the cream and let cool.

   BowlPlastic wrap

To assemble

1. 8
   Preheat the oven to 200°C (390°F) and line a sheet pan with parchment paper.

   ⚙ Preheating the OvenOven

   💡Put things in the oven only once it's reached temperature, after the heating light has gone off: an oven that hasn't reached temperature changes baking times, and the bake burns outside or stays underbaked.
2. 9
   Cut the pastry into three equal layers and place them on the baking sheet.

   KnifeBaking sheet
3. 10
   Bake 20 minutes, until the layers are browned and crisp.

   ⚙ BakingOvenBaking sheet

   💡Check by the cue (until…), not just the clock: every oven bakes a little differently.
4. 11
   Let the pastry layers cool.

   Cooling rack
5. 12
   Whip' the cream and powdered sugar' to stiff peaks.' Fold it into the cold cream with gentle strokes.'

   ⚙ WhippingBowlHand mixerorStand mixerorWhisk

   💡Whip cream very cold, in a chilled bowl with chilled beaters, and stop when it holds firm: overwhipping turns it grainy and buttery.
6. 13
   Assemble: a layer of pastry, a layer of cream, a layer of pastry, a layer of cream and a layer of pastry on top.

   Offset spatula

   💡Assemble only with completely cold cream and cooled layers: warm cream softens the puff pastry, and it loses its crispness.
7. 14
   Pour the melted white chocolate over the top pastry layer and smooth it, pipe lines of the melted dark chocolate over it and drag a toothpick across the lines for a marble pattern.

   Offset spatulaToothpick
8. 15
   Chill 2 hours before cutting.

   Refrigerator

   💡Chilling sets the cream: a cake that has chilled long enough cuts with a serrated knife without the cream squeezing out the sides.