Chocolate Opera Cream Cake Recipe

Prepare and heat oven

Preheat the oven to 200°C (400°F). Line a 12x18 inch (or similar half-sheet) baking pan with parchment paper and lightly grease.

Whip egg whites

In a clean, dry bowl, whip 4 egg whites until foamy. Gradually add 2 tablespoons granulated sugar and continue whipping to medium-stiff peaks. Set aside.

Beat eggs and sugar

In a separate bowl, whisk together 4 whole eggs and 100 g granulated sugar until pale and slightly thickened (ribbon stage), about 3–4 minutes by hand or 2–3 minutes with a mixer on medium speed.

Fold dry ingredients

Sift together 50 g all-purpose flour and a pinch of salt. Fold the ground almonds (100 g) into the egg and sugar mixture, then gently fold in the sifted flour until mostly incorporated.

Combine with whites and butter

Fold one-third of the whipped egg whites into the batter to lighten it, then gently fold in the remaining whites until homogeneous. Fold in 40 g melted butter (cooled slightly) and 1 tsp vanilla extract until just mixed. Avoid overmixing to keep volume.

Bake

Spread the batter evenly into the prepared pan (about 1 cm/3/8" thick). Tap the pan once to level. Bake at 200°C (400°F) for 8–10 minutes, until lightly golden and springy. Remove from oven and allow to cool slightly in pan for 5 minutes, then turn out onto a rack and peel off parchment. Cool completely.

Trim and cut layers

Once cooled, trim edges to create a clean rectangle. Using a ruler and a sharp knife (or a serrated blade), cut the sponge into three equal rectangular layers (for a 3-layer opera: bottom, middle, top). If your pan produces one large sheet, cut into 3 strips of equal height. Reserve.

Combine 120 ml strong brewed espresso and 30 g granulated sugar in a small saucepan over medium heat. Stir until sugar dissolves. Remove from heat and stir in 15 ml dark rum or coffee liqueur if using. Cool to room temperature. Use to brush sponge layers to infuse coffee flavor.

Make ganache

Place 220 g chopped bittersweet chocolate in a heatproof bowl. Heat 200 ml heavy cream to simmering (do not boil) and pour over the chocolate. Let sit 2 minutes, then stir gently from center until smooth and glossy. Stir in 20 g room-temperature butter until incorporated. Let cool until spreadable but still pourable for glaze (for filling, cool a bit more to thicken). If making a separate thinner chocolate layer for between cakes, reserve about 80–100 g of this ganache and chill slightly before spreading.

Prepare sugar and whites

Combine 4 egg whites and 200 g caster sugar in a heatproof mixing bowl (or the bowl of a stand mixer). Place the bowl over a pot of simmering water (double boiler) and whisk constantly until the mixture reaches 71°C (160°F) and is warm, glossy and sugar is dissolved (about 3–5 minutes). If no thermometer, rub a little between fingers—no grit should be felt.

Whip meringue

Remove bowl from heat and attach to stand mixer. Whip the mixture on high speed until it holds firm, glossy peaks and has cooled to room temperature (about 8–12 minutes).

Add butter and coffee

With the mixer on medium speed, begin adding 250 g soft butter, a few pieces at a time, allowing each addition to incorporate before adding more. Dissolve 2 tsp instant espresso powder in 1 tsp hot water (or 5–10 ml) and add along with 1 tsp vanilla and a pinch of salt. Continue beating until smooth and silky. If the buttercream looks curdled or loose, keep beating; if too warm, chill briefly (5–10 minutes) and continue. Taste and adjust coffee intensity.

Heat 50 ml heavy cream with 1 tsp instant espresso powder until steaming. Pour over 50 g chopped dark chocolate, let sit 1–2 minutes, then stir until smooth. Cool slightly until spreadable. This creates a thin coffee-chocolate layer to add between sponge and buttercream for extra structure and flavor.

Prepare work surface

Place the bottom sponge layer on a flat board or cake lifter. Using a pastry brush, generously brush the coffee syrup over the sponge until moist but not soggy (reserve syrup).

Layering 1 — chocolate ganache

Spread a thin, even layer (about 3–4 mm) of cooled chocolate ganache over the brushed sponge. Chill briefly (5–10 minutes) to set if needed.

Layering 2 — coffee buttercream

Pipe or spread an even layer (about 5–7 mm) of coffee Swiss buttercream over the ganache. Smooth carefully with an offset spatula to get straight edges.

Repeat and finish assembly

Place the second sponge layer on top, brush with coffee syrup, then spread the thin coffee ganache layer and a layer of buttercream as before. Top with the final sponge layer, brush with syrup. Press gently to compact the cake but do not squeeze out layers. Chill the assembled cake for 20–30 minutes to firm up.

Trim and chill

Trim the edges of the cake with a sharp knife to create clean, even sides. Place cake back in fridge to chill another 20 minutes so final glazing is neat.

Glaze with chocolate ganache

Warm the reserved portion of the chocolate ganache if necessary so it's pourable but not hot (about 30–35°C). Pour over the top of the cake, spreading quickly to cover top and letting the excess drip down sides. Smooth edges with a spatula to create a sharp finish. Refrigerate for 10–15 minutes to set the glaze.

Final touches

If desired, heat 2 tbsp apricot jam and brush very lightly on the sides before glazing for extra sheen, or dust a little cocoa powder on top. Chill until serving. For best flavor, allow cake to sit at room temperature 15–20 minutes before slicing with a hot, dry knife for clean slices.