Contents
Six or seven layers, no more than 4 cm tall in total: almond joconde soaked in coffee syrup, coffee buttercream, chocolate ganache, repeated, and finished with a mirror glaze and the word Opéra written on top in chocolate. Dalloyau in Paris standardised it in 1955, though Gaviller and others made versions earlier.
It is the most exacting cake on this site, and it is exacting in a specific way: every layer must be level, because the cake is judged in cross-section.
What makes it work
- Joconde, not genoise. A thin almond sponge baked on a sheet pan — almond flour keeps it flexible and moist enough not to need much soak.
- Everything is built in a frame on a flat board, then chilled hard and trimmed with a hot knife so the edge shows the strata cleanly.
- Chill between every layer. Twenty minutes each. Buttercream spread onto soft ganache is how the layers merge into mud.
- Coffee in three places — the syrup, the buttercream, and often the glaze. See coffee.
- Trim the edges last, with a blade heated in hot water and wiped dry. This step is what makes it look like a pastry-shop cake.
Ingredients
One 20 cm square, seven layers. Serves 16.
Joconde (one 30 × 40 cm sheet, cut into three):
- 150 g ground almonds
- 150 g powdered sugar
- 4 eggs
- 40 g all-purpose flour
- 4 egg whites
- 30 g caster sugar
- 30 g unsalted butter, melted
- 2 g fine salt
Coffee syrup: 100 ml strong espresso · 50 g sugar
Coffee buttercream: 3 egg yolks · 120 g sugar · 50 ml water · 250 g butter · 2 tbsp instant espresso dissolved in 1 tbsp hot water
Ganache: 200 g dark chocolate · 200 ml double cream · 30 g butter
Glaze: 150 g dark chocolate · 30 g neutral oil
Method
Heat the oven to 220 °C / 425 °F. Whip the ground almonds, powdered sugar and whole eggs for five minutes until light, then fold in the flour. Whip the whites with the caster sugar to soft peaks and fold in, followed by the melted butter. Spread on a lined 30 × 40 cm sheet and bake 7–8 minutes. Cool, then cut into three 20 cm squares.
Make the syrup, the buttercream (yolks whipped, 118 °C syrup poured in, butter beaten in, coffee added) and the ganache (hot cream over chocolate, butter stirred in) and let each come to spreading consistency.
Assemble on a board inside a 20 cm frame: joconde, syrup, half the buttercream, chill 20 minutes. Joconde, syrup, all the ganache, chill. Joconde, syrup, the rest of the buttercream, smoothed absolutely level. Chill one hour.
Melt the glaze chocolate with the oil, cool to 30 °C, and pour a thin layer over the top. Chill 20 minutes.
Trim 5 mm from each edge with a hot knife.
Notes
- Make it over two days. Joconde and ganache on day one; assembly and glaze on day two.
- The classic proportions are strict: seven layers, and the finished cake no taller than a fork's tine length.
- Keeps four days refrigerated, and should stand 30 minutes before serving.
Elsewhere on the site
Method and theory: Cake recipes · cakes · Types of Frostings · coffee
Nearby: dobos torte · sachertorte · genoise