Saint-Marc

Edit: here I am again a few years later with a new version of this cake; in the meantime, I have been able to taste this dessert in several pastry shops, and my new recipe is closer to what I have tested (and moreover, it is easier to make!).

A few days ago, it was my mother-in-law's birthday, and for the occasion, she asked me for a Saint-Marc. For those who don't know, it is a dessert composed of two layers of joconde biscuit, between which there is a chocolate mousse and a vanilla chiboust cream. Apparently created in the 1970s, there are several versions but no official recipe. After some research, I found on a forum (boulangerie.net) part of Mr. Peltier's recipe published in Thuriès magazine No.12. It provided the proportions for the chiboust cream, which you'll find below, but not the recipe for the other two elements. So, I used the joconde biscuit from Jacques Genin's Opera and the chocolate mousse recipe from Fashion Cooking's Royal. The result, a fresh and well-flavored dessert, was enjoyed by the whole family, so I'm sharing my version of this cake below :-)

Equipment:
Mini offset spatula
Perforated baking sheet
22cm ring
Rhodoid
Kitchen blowtorch

Ingredients:
I used Koro almond powder: code ILETAITUNGATEAU for 5% discount on the entire site (non-affiliated).
I used Madagascar vanilla from Norohy & Caraïbes chocolate from Valrhona: code ILETAITUNGATEAU for 20% discount on the entire site (affiliated).

Preparation time: 50 minutes + 10 minutes cooking time
For a cake of 20 to 22cm diameter:

Joconde biscuit:

100g eggs
80g icing sugar
80g almond powder
16g butter
25g flour
100g egg whites
32g caster sugar

Melt the butter and let it cool.
Prepare a French meringue: whip the egg whites. When they begin to foam, add 1/3 of the caster sugar while whisking slowly. Once the sugar is incorporated, add the second third, then the third. At the end, increase the whisk speed to obtain a nice smooth and shiny meringue.

Whip the eggs with the icing sugar until you obtain a well-whitened and fluffy mixture that makes the ribbon.

Then add the almond powder.

Next, fold in the French meringue and then the sifted flour.

Finally, add the melted butter (to prevent the mixture from deflating, I take a small part that I mix with the butter before incorporating this mixture into the batter), then pour onto a baking sheet covered with parchment paper to about 1cm thickness.

Bake for 8 to 10 minutes at 200°C.
Once out of the oven, reserve the biscuit on a rack.

Next, cut out a circle the size of your ring. Place the biscuit at the bottom of the ring previously lined with rhodoid.

Chocolate mousse:

300g heavy cream at 35% fat
60g whole milk
120g dark chocolate at 66%

Melt the chocolate.

Heat the milk, then pour it over the melted chocolate, mixing well with a spatula to obtain a smooth and glossy ganache.

When the ganache is around 35°C, whip the cream into a not-too-firm chantilly.

Gently fold it into the ganache.

Pour the mousse immediately over the joconde biscuit, smooth the surface, and let rest in the refrigerator.

Vanilla chantilly:

275g heavy cream at 35% fat
30g icing sugar
1 vanilla bean

Whip the cream into chantilly with the seeds from the vanilla bean. When the chantilly begins to thicken, add the icing sugar.

Pour the chantilly over the chocolate mousse, smooth the surface, and let rest in the refrigerator.

Vanilla sabayon:

1 egg yolk
20g sugar
1 teaspoon vanilla aroma
30g heavy cream at 35% fat
Brown sugar for caramelization

Whisk the egg yolk with the sugar and vanilla.

Place the mixture over a bain-marie and whisk until the sabayon reaches 70°C. The mixture should lighten and thicken.
Let cool, then whip the cream into chantilly, and fold it into the previous mixture.

Spread the sabayon over the vanilla chantilly, then let rest in the refrigerator.

Then, sprinkle with brown sugar and caramelize the surface, as for a crème brûlée. Be careful not to leave the flame on too long, as it may melt the chantilly. After caramelization, return the Saint-Marc to the refrigerator for at least 1 hour (if you wait less, your vanilla chantilly will hold less well as mine did), then unmold and enjoy!