Friday, May 31, 2013

Opéra Cake

Yesterday I spend the better part of the day making little Opéra cakes. I first had them in France and then had one from Pêche Pâtisserie in Maraval earlier this month. It's made of almond cake, coffee syrup, coffee buttercream, chocolate ganache and chocolate syrup. Each bit was made individually and then the cake was assembled. There are eggs in this thing, both raw and cooked (like tiramasu).

The time frame listed on most websites is a lie. At least I did not take two hours. Ideally the syrup and buttercream require instant espresso powder but I couldn't find it. I used twice the amount of coffee powder in the syrup but the same amount in the buttercream (because it's not that sweet and I didn't want it bitter and gross). I used a cookie sheet, 10" x 15" as the pan for the cake. I buttered the pan and put silicone covered parchment paper on it, folded over at the edges. I did not need to butter the pan. If silicone parchment paper isn't available, butter and flour the parchment. I had extra everything except the cake, so I will probably make it again next week.


Almond sponge cake
3 tbsp sifted cake flour (not self-rising), 2 eggs at room temperature, 1 cup almond flour (3 1/2 oz.), 1/2 cup sifted confectioners sugar, 2 large egg whites at room temperature, 1/8 tsp cream of tartar, 1/8 tsp salt, 1 tbsp granulated sugar, 2 tbsp melted unsalted butter (cooled to room temperature).

Coffee syrup
2 tsp instant coffee powder, 1/2 cup plus 1 tbsp water, 1/2 cup granulated sugar

Coffee buttercream
2 tsp coffee powder, 1/4 cup plus 1 tablespoon water, 6 tbsp granulated sugar, 2 large egg yolks, 1/2 cup unsalted butter (cubed and softened)

Chocolate ganache
4 oz. Hershey semi-sweet chocolate chips, 1/4 cup plus 2 tbsp heavy cream, 1 tbsp unsalted butter at room temperature

Chocolate glaze
6 tbsp unsalted butter, 7 oz. Hershey semi-sweet chocolate chips.


Almond sponge cake
1. Put oven rack in middle position and preheat oven to 425°F. Butter baking pan, then line bottom with a sheet of parchment or wax paper, leaving a 1-inch overhang on short sides, and generously butter paper. Dust pan with cake flour, knocking out excess.
2. Beat whole eggs in a large bowl with a handheld electric mixer at high speed until eggs for 2 to 3 minutes. Reduce speed to low, then add almond flour and confectioners sugar and mix until just combined. Resift cake flour over batter and gently fold in with a spatula.
3. Beat egg whites in a bowl with cleaned beaters at medium speed until foamy. Add cream of tartar and salt and beat until whites just hold soft peaks. Add granulated sugar, then increase speed to high and beat until whites just hold stiff peaks.
4. Fold one third of whites into almond mixture to lighten, then fold in remaining whites gently but thoroughly. Fold in butter, then pour batter evenly into baking pan, spreading gently and evenly with offset spatula and being careful not to deflate (batter will be about 1/4 inch thick).
5. Bake until very pale golden, 8 to 10 minutes, then cool in pan on a rack 10 minutes.
6. Loosen edges of cake with spatula, then transfer cake (on paper) to a cutting board. Cut cake into three equal rectangles, then carefully peel the cake from the paper and set back on paper to cool.

Coffee syrup
1. Stir together coffee powder and 1 tbsp water until powder is dissolved.
2. Bring sugar and remaining 1/2 cup water to a boil in a small saucepan, stirring until sugar is dissolved. Reduce heat and simmer syrup, without stirring for 5 minutes. Remove from heat and stir in coffee mixture. Let cool.

Coffee buttercream
1. Stir together coffee powder and 1 tbsp water until powder is dissolved.
2. Bring sugar and remaining 1/4 cup water to a boil in a very small heavy saucepan, stirring until sugar is dissolved. Boil, without stirring, until syrup reaches the soft-ball stage.
3. While syrup boils, beat yolks in a large bowl with cleaned beaters at medium speed for 1 minute. I would recommend using a standing mixer because the buttercream may take a while.
4. Add hot syrup to yolks in a slow stream (try to avoid beaters and side of bowl), beating, then add coffee mixture and beat until completely cool, approximately 3 to 5 minutes.
5. Beat in butter, 1 piece at a time, and beat until thickened and smooth. Store in the refrigerator until needed.

Chocolate ganache
1. Heat cream in a small pan over medium heat until just simmering.
2. Pour over chocolate; let stand about 30 seconds, then stir.
3. Whisk in butter until completely mixed. Let cool until spreading consistency.

Chocolate glaze
1. Melt butter and all but 2 tbsp chopped chocolate in a double boiler or in a metal bowl set over a saucepan of barely simmering water, stirring occasionally, until smooth.
2. Remove top of double boiler and stir in remaining 2 tablespoons chocolate until smooth, then cool glaze until room temperature but still liquid.
3. Put in a pastry bag with a small tip when ready to use. This can be stored in the refrigerator and reheated on a double boiler when needed.

To Assemble

1. Place one cake layer on a clean piece of parchment paper on the cutting board.
2. Gently brush 1/3 of coffee syrup over cake; spread.
3. Using a spatula, spread coffee buttercream over top up to 1/4 inch high.
4. Place another cake layer on top, brush on 1/3 of the syrup, and spread chocolate ganache over top to 1/4 inch height.
5. Add third layer, brush on remaining syrup, and smoothly spread buttercream over top as before. Refrigerate the cake so the buttercream can harden before the syrup is added, at least 30 minutes.
6. At least two hours before serving, pipe the syrup and use a spatula to spread it to completely cover the top. Refrigerate until the glaze is set, about 1/2 to 1 hour.
7. Trim the edges, and cut cake into 1 1/2 inch squares (or whatever preferred size) using a warm serrated knife (dip in hot water after each cut, and quickly wipe dry, to make sure the slices are very clean). Store in the refrigerator. Keep chilled until ready to eat.

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