This is a wonderful example of the simple delight that is sponge cake: a delicate vanilla sponge cradling creamy, fruity Bavarian cream and accented by tart guanabana curd. Guanabana, you ask? Why, yes! It's actually not as exotic as you might think and is available in cans of "nectar" in the international sections of most grocery stores. The taste is a cross between a strawberry and a pineapple, just a little more tart. And what makes this cream Bavarian? Must you yodel to it as you stir? Sadly, no. It's merely the addition of gelatine to a traditional pastry cream. The ripest berries in season are crucial, so you should feel free to swap out the blues I suggest for other varieties. Each element's flavour and colour sing without overpowering one another, the sponge both playing host to the filling and providing structure to the beautiful layers.
Makes 1 (8-inch / 20-cm) cake
FOR THE SPONGE CAKE:
7 eggs, at room temperature
1 cup (200 g) granulated sugar
½ teaspoon salt
2 cups (250 g) all-purpose flour
¼ cup (55 g) unsalted butter, melted
1 teaspoon vanilla extract
FOR THE GUANABANA CURD:
2 teaspoons powdered gelatin
1½ cups (360 ml) guanabana juice, divided (from one 12-ounce /
360-ml can; I use Goya brand)
1½ cups (300 g) granulated sugar
14 egg yolks
4 tablespoons unsalted butter
FOR THE BAVARIAN CREAM:
1 cup (240 ml) whole milk
2 cups (480 ml) heavy cream, divided
6 egg yolks
½ cup (100 g) granulated sugar
¼ cup (30 g) cornstarch
1 teaspoon orange extract
1 teaspoon powdered gelatin
3 cups (570 g) fresh wild blueberries, divided
FOR THE BUTTERCREAM:
1 cup (200 g) sugar
¼ cup (60 ml) guanabana juice
5 egg whites, at room temperature
1 pound (455 g) unsalted butter, at room temperature
1 to 2 drops orange gel food coloring
FOR THE ASSEMBLY:
1 cup (190 g) fresh wild blueberries
Make the sponge cake:
Preheat the oven to 350°F (175°C). Prepare two 8-inch(20-cm) round cake pans by lining the bottom of each with a round of parchment paper and spraying with nonstick cooking spray.
In the heatproof bowl of a stand mixer, combine the eggs, granulated sugar, and salt and gently whisk to break apart the eggs. Place the bowl over a saucepan of simmering water and whisk constantly until the sugar has completely melted and the mixture is warm to the touch.
Remove the bowl from the saucepan and, using a stand mixer fitted with the whisk attachment, whisk until the egg mixture is light and fluffy and the bowl is cool to the touch.
Sift the flour over the egg mixture and, using a large rubber spatula, gently fold the flour into the eggs. In a small bowl, stir together the melted butter and vanilla extract, pour the mixture over the batter, and gently fold it in until completely integrated.
Divide the batter between the two prepared pans and bake for 20 minutes, or until the cakes are golden brown and spring back when you gently touch them. Set aside to cool completely. Gently run a sharp paring knife around the edges of the cakes and turn them out onto a cooling rack.
Make the guanabana curd:
In a small bowl, sprinkle the gelatin on top of ¼ cup (60 ml) of the guanabana juice and let it sit until it has bloomed (the gelatin will become saturated and look soggy). Set aside.
In a heatproof metal bowl, combine the remaining guanabana juice, the granulated sugar, and egg yolks. Place the bowl over a saucepan of simmering water and cook, whisking constantly, until the mixture forms ribbons when you lift the whisk, about 15 minutes. Remove the bowl from the saucepan, immediately add the gelatin, and whisk until it is completely dissolved. Add the butter and whisk until it is fully incorporated.
Transfer the curd to a bowl and cover with plastic wrap, pressing the plastic directly onto the surface to prevent a skin from forming. Refrigerate until set, about 2 hours.
Make the Bavarian cream:
In a saucepan, combine the milk and 1 cup (240 ml) of the cream and bring to a simmer over medium heat.
Meanwhile, in the bowl of a stand mixer fitted with the whisk attachment, combine the egg yolks, granulated sugar, cornstarch, salt, and orange extract. Whisk on high speed until the mixture is pale and ribbons when you lift the whisk. With the mixer on medium speed, slowly pour the hot milk mixture down the side of the bowl and whisk until combined.
Scrape the mixture back into the saucepan and whisk over medium heat until the pastry cream thickens to the consistency of ketchup. Transfer the mixture to a clean mixing bowl and cover the top completely with plastic wrap, making sure the wrap adheres to the top of the pastry cream to keep a skin from forming. Set aside.
Place ¼ cup (60 ml) lukewarm water in a small microwavesafe bowl and sprinkle the gelatine evenly over the surface to bloom (the gelatine will become saturated and look soggy), about 3 minutes. Microwave the mixture at 50% power in 5-second intervals, swirling the bowl in between, until the gelatine has completely dissolved.
Bring the pastry cream to room temperature. Stir together a heaping tablespoon of the pastry cream and the gelatin, stirring to combine completely; note that the gelatin will seize and clump if the pastry cream isn't at room temperature. Stir in the remaining pastry cream. Cover the pastry cream-gelatin mixture with plastic wrap and place over a bowl of ice, stirring every few minutes, until the gelatine just begins to set and the mixture thickens slightly.
In the bowl of a stand mixer fitted with the whisk attachment, add the remaining 1 cup (240 ml) cream and whisk until soft peaks form.
Gently fold one-third of the pastry cream-gelatin mixture into the whipped cream. Add the remaining pastry cream-gelatin mixture and fold into the cream until no white
streaks remain. If the top of each cake has domed during baking, use a long and very sharp serrated knife to level it. Using a ruler (or just by eyeballing it), cut each cake horizontally into two even layers. Place a single cake layer on a serving platter and top with ½ cup (65 g) of the guanabana curd. Using a small offset spatula, spread the curd thinly and evenly. Top evenly with 1 cup (190 g) of the blueberries. Transfer one-third of the Bavarian cream to the layer and spread very evenly over the curd and blueberries. Freeze for 10 minutes to stabilize.
Repeat with the next two layers-cake, curd, blueberries, and Bavarian cream-freezing for 10 minutes between layers to stabilize.
Top with the last layer of cake and press very gently to adhere. Use a large offset spatula or a bench scraper to remove any filling that may have oozed onto the side of the cake. Wrap tightly with parchment paper (this may take a few pieces) and use tape to keep the parchment cocoon in place. Freeze for at least 2 hours or overnight, to set completely. Make the buttercream: In the bowl of a stand mixer, combine the sugar, guanabana juice, egg whites, and salt. Whisk the sugar-egg white mixture over a bain marie (a saucepan half filled with simmering water) until the sugar has completely melted and the temperature of the mixture has reached at least 160°F (72°C; it will likely go far over, but you want to ensure you reach 160°F / 72°C to kill any bacteria in the raw egg whites). Transfer the bowl to the stand mixer fitted with the whisk attachment and whisk on high until the meringue has quadrupled in volume and the bowl is cool to the touch. Add the butter, a few tablespoons at a time, until the mixture thickens and becomes a smooth, spreadable icing. You may not need all the butter.
Cover the cake with a smooth, even layer of the buttercream (see pages 68-69). Top decoratively with blueberries. Allow the cake to thaw for at least 2 hours before serving.
A NOTE FROM THE SWEET TALKER:
Some tips on eggs. First, I always use organic, freerange eggs. (Actually, I use my own hens' eggs, so I know for a fact that they are organic and free range.) I also know my hens' diet includes large doses of croissants and yummy cake crumbs, which make their egg yolks a rich, marigold orange. But despite the fact that each hen receives the same amount of food and their eggs all Have glorious, sunshiny yolks, each hen ends up laying a different size of egg. Thankfully, I am in possession of some very useful information: the correct weight of a egg. In baking, eggs are Used (not medium, not extra large, not jumbo). My hens frankly don't care that I'd like a bit of uniformity, so I end up weighing the eggs each time. For a egg, the white should weigh just a little over 1 ounce (30 g), while the yolk is .6 ounce (18 g). Here's the trick for separating eggs: They should be cold. Very cold. The chance of a yolk breaking during separation grows exponentially higher as an egg becomes warmer. However, when you use eggs in baking, you want them to be at room temperature. A room-temperature egg reaches full volume much faster than a cold egg. So, it's best to separate the cold eggs, then wait 30 minutes before using them so they have time to warm.
Bake It Like You Mean It, Published by Stewart Tabori & Chang, Photography by Tina Rupp, £18.99; www.amazon.co.uk