chestnut mont blanc

I got very chatty in this post. Maybe because I had so many pictures and well I guess I needed to balance it with some words. (Words. Sigh.)

Additionally, I’m intending to submit this to Fiesta Friday, which I discovered through link following. Me stumbling upon it and making something a bit more excessive and celebratory than usual happened to coincide, so I suppose I may as well!

Like most things in life, I was first introduced to a Mont Blanc through anime and manga (Yumeiro Patissiere indubitably played a part). And the first time I tried a version of this cake in 3D was at a Japanese-Italian bistro with a whole glass of lightened chestnut cream. I loved it, of course!

I decided to try to make a more traditional Mont Blanc—but looking at what I could find, I still had no idea what the ideal (I ditched my intent to go for traditional after seeing all the different options) Mont Blanc should be.

For reference, here are some of the recipes I reviewed for inspiration:

Bravetart’s tartshell, Runny’s over a sponge cake, this one using meringue as a base, this one that may just be the original original, this square-shaped one courtesy of NoRecipe, Uncasual Patisserie’s full size version, beautifully shaped ones from Daily Delicious, sable Breton-based from the Sweet Spot (they also perfectly summarize my own confusion on all the possibilities), and the as always impeccable Canelle et Vanille.

After a month or so of on and off deliberation, I thought I may as well start and went with what seemed good at the moment.

I ended up making the sponges twice. The first set turned out tough and bready—I had added much too much flour turning it into a gluten-ridden mess that I only managed to further strengthen as I attempted to fold in the egg whites. The second time I adapted the amount of flour and beat the eggs together instead of separately (mostly because I had an egg that I had failed to successfully separate in the fridge). The chestnut flour I used in the sponge cake is very nice by the way. I wasn’t sure it would be noticeable, or that it would manage to carry any chestnut flavour, but it did.

I also learned some fun things about gelatin: more specifically, a way to quantify their “setting power” (which is known as “bloom”) and consequently a way to interconvert between different gelatins.

Modernist Cuisine explained a handy formula; to achieve the same “setting power” your amount of gelatin and bloom are inversely proportional. In other words, mass(B)bloom(B) = mass(A)bloom(A).

The recipe I adapted the crème diplomat from (Thomas Keller and Sebastien Rouxel’s Bouchon Bakery) used silver leaf gelatin sheets, with a bloom of 160. I wanted the equivalent of 0.5 g sheet gelatin (for a quarter recipe) in Knox powdered gelatin, with a setting power of 225.

Therefore, mass of Knox = (0.5 g)(160)/225 = 0.35 g.

I was excited until I realized that there was only a 0.15 g difference, that my scale only read to 1 g, and so the best estimation I could come up with was 0.5 g by halving the 1 g I measured. Oh well!

But for future reference, the conversion factor between the two (by mass) is approximately 0.7 (to go from silver to Knox). Or, since every sheet is 2.5 g, 1.8 g powdered per sheet. And since an envelop of Knox is around 7 g, this is (I’m having too much fun…) 0.25 envelopes powdered gelatin per sheet or 4 sheets per envelope. This is not too far off David Lebovitz’s recommendation of 3.5 sheets per envelope.

For the chestnut cream, I wanted something quite firm with a lot of body so it would hold the strands well. For that reason I went with almost pure chestnut puree.

I’m not sure whether it’s evident from the pictures, but the piping bag with the chestnut cream suffered a great deal. While they’re supposed to be disposable piping bags, you can hardly use it once and throw it out without feeling wasteful; I tend to wash and reuse them until something breaks. This time, finally something did. I noticed that the bag already had a horizontal split, but it wasn’t along the seam so it seemed sufficient to patch it up with some packing tape. As I was piping the tape popped off. Muttering expressions of frustration I covered it up again only to have the bag split against the metal edge of the piping tip. This time I wisely decided to a pull half a foot of tape, unintentionally picking up an errant sheet of plastic wrap and securing it to the piping bag in the process. I heard a third ominous pop as the other side of the bag split—at this point the only reason the piping tip was still attached was thanks to my excessive taping. So you see? Troubleshooting, right there.

The multi-strand tip (or even better, Mont Blanc tip) is really useful to have. I couldn’t imagine what it must be like to pipe with a single strand tip (piping would take three times as long and require three times the length of tape, I suppose). That being said, just as I was thinking that one of the three holes on the tip began to clog. Luckily I was on my last cake by the time the second hole clogged and the chestnut cream began to determinedly work its way through the packing tape. How do you even dislodge pieces that clog the tip??? You can’t push it back into the pastry bag as it’ll just return to clog the tip again…

Recipe notes:

In the end I made 5 fully assembled Mont Blanc. I’ve noted approximately how much each component yields, but as a general rule if you want 4: halve the cake recipe and use a full recipe of the remaining components. If you want 8: use a full cake recipe, double the crème diplomat, chestnut cream, and at least 1.5x the chocolate ganache.

There are a lot of components, but they can all be made ahead of time. I made this cake over two days, making the sponge cake and pastry cream the day before, then finishing the crème diplomat and everything else the next day.

In retrospect, I wish I had added more chestnut. However the cake I made is quite manageable for those who are not too fond of chestnut. Next time though I might consider replacing the crème diplomat (which I still enjoyed) with chestnut puree lightened with whipped cream; I think the traditional one (although I’m certainly not certain) has whipped cream filling up the middle.

Also, a Mont Blanc tip looks like this:

Image source

The closest I had was a three hole piping tip which I thought worked pretty well. But that Mont Blanc tip would make the whole process a dream.

Chestnut sponge 

My starting point was the Old Fashioned Sponge Cake at Poires au Chocolat. Makes 8 small sponge cake bases.

• 2 eggs
• 80 g sugar
• 15 g chestnut flour
• 57 g flour
• 25 g butter, melted and cooled

Preheat the oven to 375F. Brush 8 4-cm tart pans with melted butter and then lightly dust with flour.

Beat eggs with the sugar until the mixture has tripled in volume, is thick, glossy, and the colour has lightened to white.

Fold a spoonful of the egg mixture into the butter until combined and fold this back into the eggs.

Sift the chestnut flour over top and fold in. Fold the flour in through two additions.

Divide into the 8 pans. Use a small offset spatula to evenly spread the batter if necessary.

Bake at 375 for 15 minutes.

Unmold as soon as they are cool enough to do so.

Rum Syrup 

Inspired from this video. Makes enough to easily glaze all cakes.

• 2 tbsp water
• 2 tbsp sugar
• small capful rum

Bring water and sugar to a boil, cook for a few moments, then remove from heat and stir in rum

Whipped ganache

Proportions borrowed from Baking by James Peterson. If you don’t want too much chocolate, you could stretch this amount out for 8. If you’d like a bit more, for 8, I would multiply the recipe by 1.5 or possibly 2.

• ¼ c cream
• 1 cap rum
• 2 oz dark chocolate, chopped

Set a glass bowl over a pot of simmering water. Add the cream and rum, heat until warm to the touch. Add the chopped chocolate and whisk until the chocolate begins to melt. Remove from the heat to finish melting the chocolate (if necessary, return to the heat).

Continue to whisk until the ganache is light, fluffy and paler in colour. This took me around 7-10 minutes; it’ll go a bit faster if your ganache is colder.

Vanilla crème diplomat

Adapted from Bouchon Bakery by Thomas Keller and Sebastien Rouxel. I had enough cream to made 5 Mont Blanc, but could have made 4 more generously portioned. To make eight, double recipe.

For the pastry cream:

• ½ c milk
• 1.5 cm length of vanilla bean
• 1 egg yolk
• 20 g sugar
• 20 g flour
• 7 g butter

For the creme diplomat:

• pastry cream as above
• 0.4 g gelatin
• 3 mL cold water
• 3 mL boiling water
• 50 g heavy cream

To make the pastry cream:

Using the tip of a paring knife, scrape the vanilla seeds from the bean. Add into a bowl. Add the egg yolk and sugar, whisk until combined. Sprinkle in the flour, whisk until pale and fluffy.

Heat the milk in a small saucepan until it begins to steam. Gradually pour into egg yolks, whisking, to temper the eggs. Return to the saucepan, throw in the length of scraped vanilla bean, and cook on medium to medium high heat. Begin by stirring with a spoon to scrape the bottom and reach the corners. Once the pastry cream begins to steam, switch to a whisk and whisk constantly as pastry cream bubbles and thickens.

I find it good to taste your pastry cream once you think its done to ensure there isn’t remnant uncooked flour taste.

Remove from the heat, whisk for another couple minutes to cool it down before adding in the butter. Add the butter in two small additions, whisking to incoporate completely.

Scrape into another bowl, cover with plastic wrap, and chill.

To make the creme diplomat:

Whip the cream in a bowl until it reaches firm peaks.

Bloom the gelatin in a small dish with the cold water; add the hot water and stir until gelatin has been dissolved. If necessary, heat a little bit.

Add a scoop of pastry cream to the gelatin and whisk until combined. Fold this back into the pastry cream and whisk until smooth.

Then fold a scoop of whipped cream into the pastry cream to lighten, followed by the remaining whipped cream.

Cover, chill for around 4 hours to let the gelatin set.

Chestnut cream

Inspired by Canelle et Vanille

• 200 g chestnut puree
• 25 g sugar
• 20 g butter

Use a stand mixer or work at it yourself with a wooden spoon, beat the chestnut puree until it appears smooth for around 10 minutes, periodically scraping the sides of the bowl. Then, press it through a fine sieve with a spatula.

Return to the mixer and beat in the sugar, and then the butter in two additions.

Beat until fluffy.

Assembly

• 1 bag roasted and peeled chestnuts
• Powdered sugar

Rewhip the ganache and chestnut cream with a whisk until malleable and smooth before using. Fill three pastry bags: 1 with whipped chocolate ganache (whatever tip), 1 with crème diplomat (large tip), and 1 with the chestnut cream (a mont-blanc tip or multi-strand piping tip, or just a small, thin circular tip).

Start with a chestnut sponge, brush lightly with rum syrup (this step could also be done earlier).

Pipe a ring of chocolate ganache, use an offset spatula dipped in hot water and then dried, to smooth out the ring (if necessary; my ganache was cold and I was using a plastic bag so my piping was disastrous).

Nestle 1 or 2 chestnuts in the middle of the ganache, depending on their size.

Surround and cover the chocolate and chestnuts with the crème diplomat, creating an even dome shape. If necessary (again, my poor piping) smooth the dome with an offset spatula. It’s good for this dome to be even in order for the chestnut puree to land nicely. Leave a good half centrimetre edge around the dome on which to rest the chestnut cream.

Then using your multi tip, pipe strands of chestnut cream around the dome of crème diplomat, right to the edge of the sponge and covering the cream entirely. Start from the bottom and work your way up. Move quickly in a circular motion and pipe from directly above in order to avoid squiggly strands. Make sure you cover the bottom nicely before moving up, as it is a bit difficult to go back and cover your tracks.

Finish with a dusting of powdered sugar.

I almost forgot–happy lunar new year!