Chocolate Crème Diplomate

As New Year’s will soon be upon us, an elegant celebration cake is in order!  If you are searching for a fancy chocolate filling for a génoise sponge cake base, chocolate crème diplomate may be the answer for you.  It is easy to make and tastes like a light, mousse-like filling.  I make chocolate diplomat cream by mixing bloomed gelatin into warm chocolate pastry cream, which I thereafter fold into whipped cream once the pastry cream cools to room temperature.  I then quickly spread the crème diplomate in a thick layer in between the cake layers before the cream sets.  While the cream forms a thick layer, it’s still light by comparison to American buttercream and pairs perfectly with génoise sponge cake given the lightness of this type of cake.  To finish the cake, I like to glaze the top and sides of the cake with chocolate ganache and sprinkle chocolate shavings on top for a simple decoration.

The recipe below was requested by a reader (thank you!) and is the recipe I used to fill the cake shown in one of the photos included towards the end of this post:  Basics: No Fail Polish Chocolate Sponge Cake (Biszkopt ciemny).  It makes a large quantity of chocolate crème diplomate and therefore works best for filling a 10-inch three-layer cake.  However, I have also used it to fill 9-inch and 9 1/2-inch three-layer cakes but needed to create a cake collar out of aluminum foil when assembling the cake.  The filling layer was very thick, much to everyone’s delight!

After the recipe below, look over the step-by-step instructions and photos showing how I made the diplomat cream and, thereafter, how I filled a 9-inch three-layer cake using an improvised cake collar.  If you want to fill a 9 1/2 or 9-inch (or even 8-inch) cake but do not want such a thick layer of filling, use 3/4 of the recipe (see recipe Notes) or use the extra filling for another purpose, like to fill chocolate shells.

Happy New Year!

Print Recipe
Chocolate Crème Diplomate
Makes 6 to 7 cups of diplomat cream to fill a 10" three-layer Polish spongecake or genoise. Recipe can also be used to generously fill a 9 1/2 or 9-inch three-layer cake. However, if reduced quantity is desired, see Notes for 3/4 recipe.
Course Basics, Cakes
Cuisine French
Keyword Cake
Servings
cups
Ingredients
  • 8 ounces dark chocolate, chopped finely
  • 0.25 ounces unflavored gelatin powder (1 envelope , about 1 tablespoon)
  • 1/4 cup water
  • 2 cups milk
  • 5 large egg yolks (or 4 extra large yolks)
  • 2/3 cup granulated sugar
  • 1/4 cup cornstarch
  • 1 teaspoon vanilla extract
  • 2 cups heavy whipping cream
Course Basics, Cakes
Cuisine French
Keyword Cake
Servings
cups
Ingredients
  • 8 ounces dark chocolate, chopped finely
  • 0.25 ounces unflavored gelatin powder (1 envelope , about 1 tablespoon)
  • 1/4 cup water
  • 2 cups milk
  • 5 large egg yolks (or 4 extra large yolks)
  • 2/3 cup granulated sugar
  • 1/4 cup cornstarch
  • 1 teaspoon vanilla extract
  • 2 cups heavy whipping cream
Instructions
  1. Place 8 ounces chocolate in medium bowl set over a small saucepan of simmering water (1/2 inch deep). Bottom of bowl should not touch water. Stir with spatula until almost melted. Remove bowl from heat and stir until all chocolate pieces have melted. Sprinkle gelatin over water to bloom (about 5 minutes).
  2. Bring milk to a boil in a medium saucepan over medium heat. While milk is heating, in a medium bowl, combine egg yolks and sugar with a whisk until smooth. Whisk in cornstarch.
  3. When milk just begins to boil, remove from heat and pour into egg yolk mixture in a stream while whisking. Pour mixture back into saucepan and cook over medium heat while constantly whisking. When mixture just comes to a boil, reduce heat to low and whisk for about 1 minute (mixture will be thick). Remove from heat and whisk in bloomed gelatin until dissolved. Transfer to a bowl and whisk in melted chocolate and vanilla extract. Press plastic wrap onto the surface of the pastry cream to prevent a skin from forming. Cool to room temperature (not in refrigerator).
  4. When chocolate pastry cream has come to room temperature, whip cream in a large bowl with an electric mixer until stiff peaks form. Fold 1/4 of the whipped cream into chocolate pastry cream with spatula. Carefully fold mixture into the rest of whipped cream until fully incorporated.
  5. Use immediately to fill cake layers. Fill cake in cake ring or springform pan. Chill filled cake until set, about 4 hours or overnight.
Recipe Notes

Use to fill No Fail Polish Chocolate Spongecake found on HollyTrail.com.

Ingredients for 3/4 recipe:  6 ounces dark or semi-sweet chocolate, chopped or chips; 2 1/4 teaspoon unflavored gelatin powder; 3 tablespoons cold water; 1 1/2 cups milk; 4 large egg yolks; scant 1/2 cup granulated sugar (i.e. 1/2 cup minus 1/6 cup sugar); 3 tablespoons cornstarch; 1 teaspoon vanilla extract; and 1 1/2 cups heavy whipping cream.  Follow directions above using these proportions.

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STEP-BY-STEP INSTRUCTIONS WITH PHOTOS

Place 8 ounces chocolate in a medium bowl set over a small saucepan of simmering water (1/2 inch deep). The bottom of the bowl should not touch the water. 
Stir the chocolate with a spatula until the chocolate is almost melted. Remove the bowl from the heat and stir until all the chocolate pieces have melted. 
Set aside while you prepare the pastry cream.
Prepare some cold water in a small bowl for the gelatin.  
Sprinkle the gelatin powder over the water to bloom (about 5 minutes).
Set the gelatin aside while you prepare the custard.
Bring the milk to a boil in a medium saucepan over medium heat. 
While the milk is heating, in a medium bowl, combine egg yolks and sugar with a whisk until smooth. Whisk in cornstarch.
When the milk just begins to boil, remove from heat and pour into egg yolk mixture in a stream while whisking.
Pour the egg/milk mixture back into the saucepan and cook the mixture over medium heat while constantly whisking.
When the mixture just comes to a boil, reduce the heat to low and whisk for about 1 minute (mixture will be thick).
Remove the mixture from the heat and whisk in the bloomed gelatin until dissolved.
Transfer the pastry cream to a bowl and whisk in the melted chocolate and vanilla extract.  Cover the chocolate pastry cream with plastic wrap and press lightly onto the surface of the cream to prevent a skin from forming.  Set the bowl aside on the kitchen counter to let the cream cool to room temperature.
When the chocolate pastry cream has come to room temperature, whip heavy whipping cream in a large bowl with an electric mixer until stiff peaks form.
Fold 1/4 of the whipped cream into chocolate pastry cream with spatula.
Carefully fold the mixture into the rest of whipped cream until fully incorporated.
Below is a photo of the finished chocolate crème diplomate.  It should be used to fill cake layers right away because once it sets, it will be hard to work with.  This quantity generously fills a three- layer cake with about an inch of filling per layer.  It also sufficiently fills a four-layer cake.  To finish the cake, I smooth the sides with a spatula and cover the top and sides with a thin layer of chocolate ganache.  I finish the cake by decorating the top rim with chocolate shavings.  [For a less sweet and rich finish, instead of applying chocolate ganache to the cake, simply dust the top with cocoa powder.]
INSTRUCTIONS ON FILLING A THREE-LAYER CAKE:
Below, I demonstrate how I filled a 9-inch chocolate sponge cake that was cut into three layers.  I baked the cake the day before in a 9-inch springform pan.  First, I spread a couple of tablespoons of apricot jam to introduce a fruity flavor but also to help moisten the cake layer, since it tends to be on the dry side.  Alternatively, sprinkle a couple of tablespoons of brandy, liqueur, or herbal tea across the cake layer.
Dollop 1/2 of the diplomat cream and spread evenly across the top, about 3 to 3 1/2 cups of cream.  It will form a very thick layer of a mousse-like cream in between the cake layers.  If you assess that using 1/2 will be too much for your cake, feel free to use less but note that you’ll have leftovers.
Cover the cream layer with the second cake layer.  Press the second cake layer into the cream layer to ensure there are no gaps.  Then spread some jam or sprinkle liqueur or tea across the top of the second cake layer.
If you see that your cake pan may overflow if you add more cream and the third cake layer, create a 3-inch cake collar with some aluminum foil (folded in half to make it stronger) or use a professional acetate cake collar.
Spread the remaining diplomat cream across the top of the second layer.
Cover the second cream layer with the third cake layer, bottom side up.  Press the cake layer into the cream layer.
Refrigerate the filled cake until the cream has set, about 4 hours, or overnight.  Remove the sides of the pan.
With a spatula, smooth the cream that seeped out in between the layers on the sides of the cake, but do not attempt to completely cover the sides with the extra cream–there won’t be enough cream.
Prepare chocolate ganache and pour over the top and sides of the cake.  To make a chocolate ganache glaze for this cake: Heat 1 1/4 cups heavy whipping cream, 1 tablespoon instant coffee powder, and 3 tablespoons corn syrup (optional) until just comes to a boil and pour over 10 ounces chocolate chips or coarsely chopped chocolate. Let stand 30 seconds. Starting from the middle, mix vigorously until emulsified. Mix in 1 teaspoon vanilla extract. Let cool slightly and then pour over cake to cover top and sides (use offset spatula to help spread the glaze onto the sides but not the top).
If sprinkling with chocolate shavings, do so before the ganache sets.
If wanting to decorate with icing, let the ganache first set.  To set the ganache, place the cake in the refrigerator, uncovered, for at least 15 minutes or until set.  Store the finished cake in the refrigerator.

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