Daring Bakers May Challenge – The Opéra Cake (Gluten-free)

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For the Syrup

½ cup water
⅓ cup granulated sugar
2 Tbsp. lemon rind (remove after syrup has cooled)

1.Stir all the syrup ingredients together in the saucepan and bring to a boil.
2.Remove from the heat and let cool to room temperature.

For the Buttercream
I used a modified version of the buttercream recipe from Dorie Greenspan’s “Perfect Party Cake”

1 cup sugar
4 large egg whites
3 sticks unsalted butter (at room temperature)
2 Tbsp. reduced blueberry juice
1 tsp. pure vanilla extract

Put the sugar and egg whites in a mixer bowl or other large heatproof bowl, fit the bowl over a pan of simmering water and whisk constantly, keeping the mixture over the heat, until it feels hot to the touch, about 3 minutes. The sugar will be dissolved, and the mixture will look like shiny marshmallow cream. Remove the bowl from the heat.

Working with the whisk attachment or with a hand mixer, beat the meringue on medium speed until it is cool, about 5 minutes. Switch to the paddle attachment, and add the butter a stick at a time, beating until smooth. Once all the butter is in, beat the buttercream on medium-high speed until it is thick and smooth, 6-10 minutes. During the time, the buttercream may curdle or separate – just keep beating and it will come together again. On medium speed, gradually beat in the blueberry juice, waiting until each addition is absorbed before adding more and then the vanilla. You should have a shiny, smooth, velvety buttercream. Press a piece of plastic against the surface of buttercream if you want to set it aside.

White Chocolate/Ganache Mousse

7 ounces white chocolate
1 cup plus 3 tbsp. heavy cream (35% cream)
rind of 1/2 lemon

1.Melt the white chocolate and the 3 tbsp. of heavy cream in a small saucepan.
2.Stir to ensure that it’s smooth and that the chocolate is melted. Add the tablespoon of liqueur to the chocolate and stir. Set aside to cool completely.
3.In the bowl of a stand mixer, whip the remaining 1 cup of heavy cream until soft peaks form.
4.Gently fold the whipped cream into the cooled chocolate to form a mousse.
5.If it’s too thin, refrigerate it for a bit until it’s spreadable.
6.If you’re not going to use it right away, refrigerate until you’re ready to use.

The Glaze

14 ounces white chocolate, coarsely chopped
½ cup heavy cream (35% cream)

1.Melt the white chocolate with the heavy cream. Whisk the mixture gently until smooth.
2.Let cool for 10 minutes and then pour over the chilled cake. Using a long metal cake spatula, smooth out into an even layer.
3.Place the cake into the refrigerator for 30 minutes to set.

Assembling the Opéra Cake

Line a baking sheet with parchment or wax paper.

Working with one sheet of cake at a time, cut and trim each sheet so that you have two pieces (from each cake so you’ll have four pieces in total): one 10-inch (25-cm) square and one 10 x 5-inch (25 x 12½-cm) rectangle.

Step A (if using buttercream only and not making the ganache/mousse):

Place one square of cake on the baking sheet and moisten it gently with the flavoured syrup.

Spread about one-third of the buttercream over this layer.

Top with the two rectangular pieces of cake, placing them side by side to form a square. Moisten these pieces with the flavoured syrup.

Spread another third of the buttercream on the cake and then top with the third square of joconde. Use the remaining syrup to wet the joconde. Spread the remaining buttercream on top of the final layer of joconde and then refrigerate until very firm (at least half an hour).

Make the glaze and after it has cooled, pour/spread it over the top of the chilled cake. Refrigerate the cake again to set the glaze.

Serve the cake slightly chilled. This recipe will yield approximately 20 servings.

Step B (if making the ganache/mousse):

Place one square of cake on the baking sheet and moisten it gently with the flavoured syrup.

Spread about three-quarters of the buttercream over this layer.

Top with the two rectangular pieces of cake, placing them side by side to form a square. Moisten these pieces with the flavoured syrup.

Spread the remaining buttercream on the cake and then top with the third square of joconde. Use the remaining syrup to wet the joconde and then refrigerate until very firm (at least half an hour).

Prepare the ganache/mousse (if you haven’t already) and then spread it on the top of the last layer of the joconde. Refrigerate for at least two to three hours to give the ganache/mousse the opportunity to firm up.

Make the glaze and after it has cooled, pour/spread it over the top of the chilled cake. Refrigerate the cake again to set the glaze.

Serve the cake slightly chilled. This recipe will yield approximately 20 servings.

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