Chocolate Mousse Mille-Feuille (Daring Bakers' Challenge)

It's October 27th!  That means it's time for another Daring Bakers' Challenge.  This month's challenge was to create something called mille-feuille, which means "thousand sheets" in French.  The reason this is called "thousand sheets" is because the buttery pastry part of this dessert is folded and rolled out a gazillion times (I may be exaggerating...a bit).  Typically, mille-feuille is filled with a vanilla pastry cream.  I felt like I'd just used pastry cream in the pâte à choux swans challenge, so I decided to use chocolate mousse instead.

Our October 2012 Daring Bakers’ challenge was hosted by Suz of Serenely Full. Suz challenged us to not only tackle buttery and flaky puff pastry, but then take it step further and create a sinfully delicious Mille Feuille dessert with it!

I found an excellent chocolate mousse recipe over at Dessert First.  It's part of a series where several different chocolate mousse techniques are tried and evaluated.  I chose this because it looked like it would set up nicely in a spring-form pan, and because the eggs are cooked (I'm afraid of uncooked eggs - probably unreasonably so).

The most time-consuming aspect of this dessert was the pastry, which, as previously mentioned, had to be folded, rolled, folded, and rolled a bazillion times.  I was especially frustrated with the numerous wait times.  So that the butter wouldn't just melt and go everywhere, the pastry had to regularly be refrigerated for about a half-hour between foldings.  This meant that my afternoon looked like: start pastry, do dishes while pastry cools, roll pastry, go to grocery store while pastry cools, roll pastry, play some Sims 3 while pastry cools, roll pastry, take a nap while pastry cools, finally bake pastry.  At work, we would call this "randomizing", and it's bad.

I wanted the mousse to set between the pastry layers instead of piping it on after it had set.  I believed this would make for a fluffier mousse and a very pretty display.  For that reason, I invested in a 6" spring-form pan from Fat Daddio's.  This decision caused some unexpected challenges.  First, it was a bit hard to cut the puff pastry so that it fit exactly into the pan.  As a result, the mousse got into all the cracks and kind of hid the pastry.  Second, my fear of the mousse sticking to the pan led me to attempt to line it with parchment paper.  This meant that instead of pretty, smooth layers of mousse, I got wrinkles (as you can clearly see in all my pictures).  Sigh...

Have some milk or coffee standing by when you finally eat this - it's super rich and chocolaty.  While the mousse dominates flavor-wise, the puff pastry gives it a nice, buttery, crispiness.  I highly recommend using a good chocolate because you will taste it.

Overall, I'm glad to have tried this dessert.  I don't know if I'll be making the "thousand sheets" pastry again anytime soon, since it was a lot of work, and I think a chocolate mousse pie would yield something very similar in a fraction of the time.  Still, I'm glad to have the experience!

Puff Pastry
Adapted from Christine Benlafquih for About.com.  This makes enough for 4 6" round layers of puff pastry.

Ingredients for Pastry
2 cups (250g) all-purpose flour
1 teaspoon salt
3½ tablespoons unsalted butter, chilled and cubed
½ cup plus 2 tablespoons ice-cold water

Ingredients for Beurrage
14 tablespoons butter, at room temperature
3½ tablespoons (30g) all-purpose flour

Method

1. To make the pastry, combine the flour and salt in a medium bowl.
2. Add the butter and cut it into the flour with your hands or a pastry cutter until it looks like soft breadcrumbs.
3. Add the cold water and mix with a fork until combined.
4. Knead the dough for about three minutes, until smooth.
5. Wrap the dough in plastic wrap and refrigerate for at least 30 minutes.
6. To make the beurrage, squish together the butter and flour in a small bowl until combined.
7. With your hands, on a sheet of plastic wrap, form the beurrage into a 4.5-inch square.  Place another piece of plastic wrap on top, and neaten up the square.
8. Refrigerate for about 15 minutes, or until the beurrage is flexible but not soft.
9. Remove the pastry dough and work it into a 6-inch square.  Place the beurrage in the middle, offset by 45°, so that the corners of the beurrage touch the sides of the pastry.
10. Fold the corners of the pastry over the beurrage and cinch it together so that it completely encases the beurrage.  
11. Alright, time for folding/rolling madness!  On a floured surface, roll the dough out into a rectangle.
12. Fold the rectangle into thirds, forming a smaller rectangle.
13. Repeat 11 and 12.
14. Wrap the dough in plastic wrap and refrigerate for at least 30 minutes.
15. Repeat 11 and 12 twice.
16. Wrap the dough in plastic wrap and refrigerate for at least 30 minutes.
17. Repeat 11 and 12 twice.  (Last time!  You can do it!)
18. Wrap the dough in plastic wrap and refrigerate for at least 30 minutes.
19. Preheat your oven to 400° F.
20. Cut a piece of parchment paper to about 12" by 18".
21. Roll the dough out onto the parchment paper, until it about covers the entire thing.
22. Poke the dough with a fork all over so that air can escape.
23. Cut the dough/paper in half if necessary so that it fits on a cookie sheet.  Slide the first half onto a cookie sheet.  Place another piece of parchment paper on top, then place another cookie sheet on top.  This is to keep the puff pastry flat.
24. Bake for about 15 minutes.
25. Remove the cookie sheet and parchment paper on top of the pastry, and bake for another 5-10 minutes, just until the pastry begins to brown.
26. Remove and allow to cool on a wire rack.
27. Repeat with the second half of the pastry.

Chocolate Mousse
Adapted from Dessert First's Custard-Based Mousse recipe.

Ingredients
180g bittersweet chocolate, chopped
1 egg yolk
1 tablespoon sugar
¼ cup whole milk
1 cup heavy whipping cream, separated

Method

1. Either in your microwave or in a double-broiler, melt your chocolate and transfer to a large bowl.
2. Whisk together your egg yolk, sugar, milk, and ⅓ cup whipping cream in a saucepan.  Stirring constantly, heat over medium until the mixture has thickened and can coat the back of a spoon (about 6-8 minutes for me).
3. Pour about a third of the hot custard through a strainer and into the chocolate.  Mix until combined.  Repeat with two more pours of the custard until the custard is completely combined with the chocolate.
4. Whip the remaining ⅔ cup whipping cream in a medium bowl until stiff peaks form.
5. When the chocolate/custard mixture has cooled to around 113-122° F, fold in the whipped cream and carefully mix to combine.
6. Assemble the pastry before the mousse sets.

Assembly

1. Either line your 6" spring-form pan with parchment paper, or coat it with something non-stick (oil or a spray).
2. Using the pan, or something else 6" in diameter, cut three or four round circles out of the puff pastry using a knife.  I only did three layers of pastry, but the recipe makes enough for four.
3. Place a pastry circle into the pan.
4. Spread either half (if you're doing 3 pastry circles) or a third (if you're doing 4) of the mousse on top.
5. Repeat steps 3 and 4.
6. If your doing 4 pastry circles, repeat steps 3 and 4 again.
7. Place your last pastry circle in the pan.
8. Top with melted chocolate (that's what I did - it proved to be hard to cut), powdered sugar, or a chocolate glaze.  If you'd like to get the cool squiggly design in melted chocolate or a glaze, pipe some melted white chocolate in lines across your dark chocolate.  With a sharp knife, trace a line alternately down and up across the lines.
9. Refrigerate for at least 12 hours to allow the mousse to set.
10. Carefully remove the top of the spring-form pan.