This is one of my wife's favorite pastries to have with her tea and coffee. I will say that I'm a huge fan as well. Mille feuille (a thousand leaves) is a classic french pastry that is made of puff pastry and mousseline cream, although with everything people make it with slight variations some use strictly pastry cream, diplomat cream, but I think the mousseline works the best. Not to mention that this recipe is adapted from Bouchon bakery book and that's what they use. I think every country makes their own version of this classic dessert. I know I have had this delicious pastry or a similar variation in El Salvador, America, France, Italy, England (they only did one layer and added strawberries), and Argentina I think we had one too. Depending on the freshness, amount of cream and the topping for me really makes the difference of who has the best and worst.
I did not make my puff pastry this time because of time constraints but hopefully have a recipe soon for puff pastry. Puff pastry is almost like croissant dough without the yeast. It is a lamented dough that when cooked produces layers of pastry. The only downside to this pastry is it always a bit hard to cut into without the filling going everywhere. In the bouchon book the serve it on its side which is really smart. I left this dessert sitting up right for this application and because I didn't serve it immediately. I also didn't make the icing on top that is typically done because of time constraints as well. I simply finished with powdered sugar. It still didn't make the pastry any less delicious.
I puff pastry ( I used pepperidge farms )
1/2 cup plus tbsp egg yolk
1/2 cup plus 3 tbsp sugar
1 small vanilla bean
1/2 cup plus 1 1/2 tbsp custard powder or ap flour
2 cups and 3 tbsp of milk
1 ounce (2 tbsp ) of butter
Basic Butter Cream
75 g (1/4 cup 1 tbsp) egg whites
150 g (3/4 cup) sugar
plus 2 tbsp plus 2 1/4 tsp) of sugar
42 g (3 tbsp 1 tsp ) of water
8 ounces (2 sticks) butter
Powdered sugar for dusting
Preheat Oven to 400 degrees
Take one half of the puff pastry and cut in 1/3's using the natural creases of the puff pastry. Place on a sheet tray lined with parchment paper. Take another piece of parchment paper and place on top of the puff pastry. Then place a second sheet pan on top of the parchment and puff pastry. The weight of the pan will not allow the puff pastry to puff up. If you want to make 2 napoleons then do the second piece of puff pastry the same way. I combined all of the pastry cream and all of the butter cream together and it is a perfect amount to make two napoleons. Otherwise you will have left over pastry cream and buttercream (which isn't a bad thing). Place the sheet pan in the oven and bake for 22 minutes or until golden brown. Take out and let it cool completely
For the pastry cream
Place egg yolks in a stand mixer with the whisk attachment. Turn on the mixer and whisk the eggs for 20 seconds. Then scrape the vanilla bean into the egg yolks. Turn the mixer back on and add the sugar gradually into the egg yolks. Once all the sugar has been incorporated turn the mixer up to high. Whisk for 3 minutes on high until the egg yolks are light and fluffy. Then add your custard or flour to the egg yolk mixture. Mix on low for 30 seconds and then turn to high for another 45 seconds. Scrape the sides of the bowl and mix for another 30 seconds.
Meanwhile in sauce pot on medium high add your milk and the scraped vanilla bean to the pot. Gently bring to a scald. Then temper the egg yolk mixture by pouring a little of the milk into the egg yolk mixture a little at a time while the mixer is running on low speed. Continue until you have half of the milk mixed into the egg yolks. Then pour all of the contents back into your pot. On low heat stir with a whisk until the egg mixture starts to thicken and lightly bubble. Once it starts to thicken cook for another 5 minutes whisking constantly. You want to make sure that you do this so that the flour taste cooks out of the mixture. Once cooked pour the mixture through a fine mesh strainer into a bowl that is set in an ice bath. Once in the bowl whisk for a minute to help cool then add your butter. Place a piece of plastic wrap directly on top of the custard to help prevent a skin from forming. Allow to cool in the ice bath or refrigerator for at least a few hours.
For the buttercream
Place water and stir in 3/4 cup of the sugar. Bring to simmer over medium high heat until the syrup reaches 230 degrees. Meanwhile place your egg whites in a stand mixer on medium speed and gradually pour in the 2 tbsp and 2 tsp of sugar whipping until they begin to form loose peaks. When the syrup reaches 248 degrees turn the mixer down to medium low and gradually pour the syrup into the egg whites. Once all incorporated turn to high and mix for 15 minutes or until the bottom of the bowl has cooled down. Once to room temperature gradually add the butter a few pieces at a time. If it ever looks broken simply increase the speed to emulsify the mixture back together. Place in the refrigerator to firm up a bit.
In the bouchon bakery book it calls for 375g of each pastry cream and butter cream to be mixed together. As earlier stated I mixed all of both creams together. Simply put the pastry cream in a stand mixer and whisk on medium speed until smooth then add your buttercream until well combined. Then take a sheet pan lined with plastic wrap. Pour the mixture onto the pan. With an offset spatula smooth out the mousseline and place in the freezer (book says overnight) I did an hour. Which was plenty firm enough for me to cut it and it stay firm.
trim the sides and ends of the puff pastry so they all are equal. Then cut the mousseline the same size as the puff pastry and place in between each layer of puff pastry. Dust the top with powdered sugar. Refrigerate for half an hour before you serve. Cut and enjoy!