Opera Gâteau Recipe

Prepare and preheat

Preheat oven to 220°C (425°F). Line two half-sheet baking pans (13x18 inches) with parchment; brush very lightly with oil or melted butter and place parchment so it doesn't move.

Make batter - stage 1

In the bowl of a stand mixer fitted with the whisk attachment, whisk the whole eggs and 90 g granulated sugar on high speed until very light, thick, and ribbon stage (about 5–7 minutes).

Fold dry ingredients

Sift together the almond flour, icing (confectioners') sugar, and all-purpose flour. Gently fold the dry mixture into the whipped eggs in two additions using a rubber spatula, taking care to retain air.

Make meringue and finish batter

In a clean bowl, whisk the 3 egg whites with a pinch of salt until foamy. Gradually add 25 g sugar and continue whisking to medium-stiff peaks. Fold one-third of the meringue into the almond-egg mixture to lighten it, then fold in the remaining meringue in two additions. Finally fold in the cooled melted butter gently until incorporated.

Bake

Spread batter evenly into prepared pan(s) to a uniform thickness (about 5–6 mm). Bake for 5–8 minutes, until the surface is set and lightly golden but not overbrowned. Remove from oven and immediately turn out onto a sheet of parchment. While still warm, trim the edges to make straight rectangles and, once cool, measure and mark layers 20 x 30 cm (approx.) to cut 4–6 even strips for assembly. Allow to cool completely, then wrap in plastic to prevent drying.

Combine the 120 ml brewed espresso and 60 g sugar in a small saucepan. Heat gently, stirring until sugar is fully dissolved. Remove from heat and stir in the optional 15 ml rum or liqueur. Cool to room temperature. Reserve for brushing sponge layers.

Cook yolk sabayon

Place the 6 egg yolks and 150 g sugar in a heatproof bowl set over a barely simmering bain-marie (do not let the bowl touch the water). Whisk constantly until the mixture reaches about 71–75°C (160–167°F) or is thick, pale, and ribbon-like (about 5–8 minutes). Remove from heat and continue whisking until cooled to room temperature (this may take 8–12 minutes).

Whip butter

In the paddle or whisk-equipped mixer, whip the 360 g room-temperature butter until pale and light in texture (2–3 minutes).

Combine and flavor

Once the sabayon is fully cooled, add it gradually to the whipped butter in 3 additions, mixing on medium speed until smooth and silky. If the mixture looks curdled, continue beating — it will come together. Mix in the 45 ml cooled espresso, 1 tsp vanilla, and a pinch of salt. Taste and adjust espresso or salt as needed. Chill briefly if too soft, then bring back to spreadable consistency by beating lightly.

Heat cream

Place the chopped chocolate in a heatproof bowl. In a small saucepan, heat 225 ml heavy cream to just below boiling (small bubbles at edge). Pour the hot cream over the chocolate and let sit undisturbed for 2 minutes.

Emulsify

Gently stir from the center outward until the mixture becomes smooth and glossy. Add the 30 g cubed butter and stir until incorporated and the ganache is shiny. Let cool at room temperature until thick but still pourable/spreadable (about 30–45 minutes depending on room temperature).

Prepare layer pieces

Trim the cooled Jaconde sponge into 4 or 5 uniform layers of equal size (classic Opera uses 4: sponge, buttercream, ganache layers repeated). Place the first sponge strip on an acetate-lined rectangular cake board, parchment, or serving tray.

Brush with syrup

Using a pastry brush, liberally brush the espresso syrup onto the sponge layer so it is moist but not soggy. Repeat for each sponge layer as you assemble.

Layer buttercream and ganache

Spread a thin, even layer (about 4–6 mm) of espresso buttercream over the first syrup-brushed sponge. Place a second sponge, press gently, brush with syrup, and spread a thinner layer of ganache (about 3–4 mm). Continue alternating: sponge (syrup) + buttercream, sponge (syrup) + ganache, finishing with a sponge topped with a thin, smooth layer of ganache. Use an offset spatula and bench scraper for sharp edges. Chill briefly (15–20 minutes) between tricky layers to firm them up for neater cuts.

Chill and trim

Once assembled, refrigerate the cake for at least 30 minutes to firm the layers. Trim edges cleanly with a sharp knife warmed in hot water and wiped dry to achieve precise rectangular edges. Optionally, score serving slices on top.

Serve

Allow chilled cake to rest at room temperature 10–15 minutes before slicing for serving. Slice into individual portions using a hot, wiped knife for clean cuts. Optionally dust ends with a little powdered sugar or decorate with a thin chocolate transfer. Keep refrigerated and consume within 3–4 days.