A napoleon or mille-feuille is a classic French pastry with layers of buttery, flaky puff pastry baked until golden and crisp, then filled with alternating layers of pastry cream. Once you learn to make this pastry at home you will never buy it at the patisserie again.
Preheat the oven at 190 C / 375 F. Cut the puff pastry into two. Roll each sheet to about 12 x 8-inch rectangle Tip - this measure is a guide but you can certainly main your own size and shape.
Work with one sheet at a time. Place on a parchment paper so it’s easy to move around.Tip - always keep puff pastry chilled or it will be difficult to work with. If necessary place in the freezer for 5 minutes for a quick chill between steps
Then cut the pastry at every 2-inch interval so you have 6 long strips. Cut each strip in half at the center so you should have 12 equal pieces. Dock the pastry with the fork and sprinkle with granulated sugarTip - docking the pastry encourages crispness, and, the granulated sugar caramelizes and gives that golden color to the baked pastry
Place a parchment paper on top. Then place a baking tray on top.Tip - the top baking tray prevents the pastry from puffing too much as well as helps make it crispy.
Bake on the center rack for 15 minutes
Remove the baking tray and parchment paper – bake another 10 minutes until lightly golden. Remove and let cool completelyTip - the final baking without the baking tray will encourage the pastry to become crisp which is what we want.
In a heavy-bottom saucepan combine sugar, cornstarch, egg yolks, vanilla bean paste, and salt. Gradually add the milk while whisking to prevent lumps.
Place the saucepan on medium heat stirring continuously until the pastry cream thickens.Tip - You want the pastry cream to come to a low simmer (boil) so the cornstarch will thicken the mixture and cookout.
Add the butter and continue to stir on low making sure to prevent the pastry from sticking or burning at the bottom.
Once the pastry cream is thick, remove from heat and pass it through a sieve or mesh. This will remove any lump and give you a smooth velvet-like pastry cream.
Cover with the plastic wrap touching the surface of the cream. Set aside to cool completely.Tip - the plastic touching the pastry cream will prevent skin from forming on the pastry cream which can later cause lumps and cause blockage in the piping bag
In the bowl of a stand mixer with the whisk attachment - whip the cream. You want nice stiff peaks.
Combine half the whipped cream to the chilled pastry cream. Use a whisk to ensure you have no lumps. Save the rest of the whipped cream for the top layer.Tip - adding whipped cream to the pastry cream will lighten it up. I highly recommend it.