Bronwen Wyatt’s Chocolate Walnut Chiffon Cake with Prunes and Chicory Cream

Chef Bronwen Wyatt‘s Chocolate Walnut Chiffon Cake is layered with prunes and chicory custard and rounded out with cocoa swiss buttercream. The flavor and texture is akin to a tiramisu – soft layers that melt in the mouth. The cake is given a New Orleans twist by substituting the typical espresso for rich roasted chicory. The prunes are soaked in cocoa chicory syrup, giving them a lovely velvety texture and enhancing the richness of the prune flavor.

This recipe has a lot of steps, but each element can be prepared ahead over the course of a few days. The cake works beautifully with your favorite gluten-free flour blend as well. Try Bronwen’s Prune Upside Down Cake with Toffee & Sesame too!

Servings: 10-12 servings
Prep Time:
Cook Time:


For the Chocolate Walnut Chiffon Cake:

  • 6 eggs, separated
  • ¼ teaspoon cream of tartar
  • ¼ cup + 2 Tablespoons (75 grams) sugar 
  • ¾ cup + 1 Tablespoon (162 grams) sugar
  • ¼ cup (30 grams) cocoa powder
  • ½ cup (60 grams) walnuts, toasted
  • 2 ¼ teaspoons baking powder 
  • 1 cup all purpose flour, or gluten-free flour blend
  • ¾ teaspoon salt
  • ¼ cup plus 2 Tablespoons (82 grams) olive oil
  • ½ cup plus 1 Tablespoon (150 grams) whole milk 

For the Cocoa-Chicory Soaked Prunes:

  • 1 cup water
  • 1 cup (200 grams) sugar
  • 1 teaspoon vanilla extract
  • 1 Tablespoon cocoa powder
  • 1 Tablespoon chicory powder (or Espresso powder)
  •  1 cup (140 grams) California prunes, chopped 

For the Chicory Diplomat Cream:

  • ½ teaspoon powdered gelatin 
  • 1 Tablespoon cool water
  • ¼ c + 1 T (58 grams) sugar
  • 1 Tablespoon chicory powder 
  • 1 Tablespoon cornstarch
  • Pinch salt
  • ¾ c (180 grams) milk
  • 2 yolks

For the Cocoa Swiss Meringue Buttercream:

  • 3 (60 grams) egg whites 
  • ¾ cup (150 grams) brown sugar 
  • ⅛ teaspoon cream of tartar 
  • ½ teaspoons salt 
  • 2 ½ sticks (295 grams) butter, cool room temperature
  • 3 Tablespoons (90 grams) cocoa powder 


For the Cake:

Preheat your oven to 350 degrees F. Set aside two 9” cake pans – springform pans would also work well. You do not need to grease or line the pans – in fact, the chiffon will rise best if the pans do not have a trace of grease. 

Measure your ingredients, taking care to keep the two different amounts of granulated sugar separate. 

Cleanly separate the eggs, taking care that no trace of yolk remains in the whites. Place the whites and the cream of tartar into the bowl of a stand mixer.

Combine the yolks and the olive oil in a bowl and whisk well. Set aside.

Take the walnuts and the larger amount of sugar and grind them until very fine in a food processor. Combine the ground walnuts and sugar mixture with the cocoa powder, baking powder, flour or flour substitute, and salt, and whisk well to combine. 

Alternate adding the flour mixture and milk to the egg yolk and olive oil mixture: add ⅓ of the flour mixture to the yolks and mix well. Add half the milk and whisk. Add another ⅓ of the flour mixture and follow with the remaining milk, whisking well after each addition. Add the last of the flour mixture and combine until there are no lumps.

Begin whisking the egg whites and cream of tartar on low speed until foamy. Slowly add the separate, smaller amount of sugar to the egg whites, a little at a time, while increasing the speed of the mixer, until your egg whites have quadrupled in volume and hold soft, shiny peaks – this process should take about 5 minutes.

Carefully fold the egg whites to the batter in three additions, taking care not to deflate the egg whites. When you no longer see a trace of white in the batter, divide the chiffon batter between two pans. 

Bake for about 40 minutes, or until the cakes have risen, and spring back lightly to the touch. After removing the cakes from the oven, turn them upside-down on a wire rack to cool. When they’ve cooled completely, run a sharp knife around the border of the cake to loosen the sides of the cake. If using a springform pan, remove the sides and carefully remove the cake from the bottom of the pan. If using a traditional cake pan, rap the pan firmly, upside down, onto your cooling rack, Your cakes should pop right out. 

The cakes can be used straight away, or wrapped well in plastic and held at room temp for up to 24 hours. They also freeze well. 


For the Cocoa-Chicory Soaked Prunes:

Combine the water, sugar, cocoa, vanilla, chicory powder in a small pot. Bring just to a boil, whisking well so that all the ingredients are combined. Pour the warm mixture over the chopped prunes and let sit for about 20 minutes (or feel free to make ahead and chill in the refrigerator for up to a week).


For the Chicory Diplomat Cream:

Note: diplomat cream is a pastry cream lightly set with gelatin, with softly whipped cream folded in. 

The chicory diplomat cream can be made up to two days ahead. 

In a medium bowl, sprinkle the powdered gelatin over the tablespoon of water. Place a strainer over the bowl.

In a small non-reactive pot, whisk together the cornstarch, chicory powder, sugar, and salt. While continuously whisking, slowly add the milk to the mixture, taking care that there are no lumps. Add the yolks and whisk to combine.

Place the pot over medium heat and warm, continuing to stir, until the mixture thickens and large bubbles begin to appear on the surface. Once you see the first bubble, continue to cook for 1 minute more (this will ensure the floury taste of the cornstarch is fully cooked off). Strain the custard into the gelatin mixture. Whisk until the gelatin is fully dissolved, and then add the cold butter a bit at a time, stirring until the butter is completely melted. Press a piece of plastic wrap to the surface of the custard and refrigerate until completely cooled, at least two hours or overnight.

When ready to complete the diplomat cream, remove the plastic wrap and gently stir the pastry cream until it is totally smooth. Whip the heavy cream until it achieves medium peaks and fold into the pastry cream, taking care not to over mix and deflate the cream. Chill until ready to use. 


For the Cocoa Swiss Meringue Buttercream:

Note: adapted from a recipe by Stella Parks  – Makes enough to (rustically) frost one 9” single layer cake

Prepare a double boiler (I use the bowl of a stand mixer over a pot of simmering water).

Cook the egg whites, sugar, cream of tartar, and salt over the double boiler until they reach 185 degrees, or are quite warm to the touch and the sugar has totally dissolved. Transfer to a stand mixer with a whisk attachment and whisk until the whites have reached firm peaks and are glossy and the bowl has cooled to the touch. Add the butter one chunk at a time until all the butter has been incorporated and the mixture is smoothly emulsified, silky, and fluffy. Add the cocoa powder and whisk at high speed to combine, scraping down the sides of the bowl with a rubber spatula so that the cocoa powder is totally combined. Taste and season with a little more salt as necessary. 


To assemble the Chiffon Cake:

Strain the prunes from the cocoa chicory soaking liquid and set aside.

Set one of the chocolate walnut cake rounds on a platter, cake stand, or cake board (whatever you’ll be using to display your cake). Brush the top of the cake very generously with the cocoa chicory syrup – you really want the cake to soak up quite a bit. Pipe a border of the cocoa swiss meringue around the edge of the cake. Sprinkle the soaked prune slices over the cake, and then mound the chicory custard over the top and spread to the edge of your cocoa buttercream border. You may have a little more than you need – set aside the remainder to serve along side your cake, as you like. Carefully place the second cake round on top. Brush the top and sides of the cake with more of the cocoa chicory syrup, and chill the cake for about 20 minutes. After it’s had time to get nice and cold, frost the cake with the remaining cocoa buttercream, making gentle swoops with a spoon or an offset spatula. Chill for at least two hours, or overnight. 

The cake should be kept cold until about forty minutes before you’re ready to serve it – it’s best at cool room temperature. 



Bronwen Wyatt of Bayou Saint Cake in New Orleans, LA., creates magical Instagram-famed cakes with local and premium ingredients – and she’s a huge fan of prunes! Additional California Prunes recipes from Bronwen include a Prune Upside Down Cake, Spiced Prune Caramel Sauce and Almond Cake with Prune-Raspberry Butter featured by Cherry Bombe media.