Opéra Cake

Make the joconde sponge. Combine the ground almonds, icing sugar, and beaten whole eggs in a bowl; mix until a uniform, slightly pale batter forms. Fold in the sifted flour, then the melted butter. Beat the egg whites separately to soft peak and fold them through the almond batter in two additions, working quickly to retain volume. Divide the batter equally across three silicone-mat-lined trays and spread to a level 5 mm. Bake at 220 °C for 8–10 minutes. The sheet is done when the surface is just set, lightly golden at the edges, and springs back at the centre when pressed.

Make the coffee syrup. Combine the cooled espresso with the sugar syrup and stir until fully incorporated. The syrup must be strong enough to flavour the sponge distinctly — taste it: the coffee should be assertive and sweet, with no raw bitterness. Set aside at room temperature.

Make the chocolate ganache (Entry 93, 1:1 ratio). Bring the cream to a near-simmer, pour it over the chopped couverture, and let it stand for one minute. Stir from the centre outward to a smooth, glossy emulsion. The ganache is ready when the surface is uniformly shiny and the mixture flows from a spoon in a single ribbon without breaking.

Make the coffee buttercream on an Italian meringue base (Entry 90). Once the meringue base is cool, beat in the softened butter in stages until the cream is smooth, pale, and holds a clean peak. Beat in the dissolved espresso powder. The buttercream is ready when it is entirely smooth, holds its shape without slumping, and the coffee flavour is distinct and even.

Cut each of the three joconde sheets in half to give six equal rectangles. Line a 30 × 20 cm frame or tray. Lay the first joconde rectangle in the base. Brush it thoroughly with coffee syrup until the sponge is visibly saturated but not pooling. Spread an even layer of coffee buttercream over the surface. Lay the second joconde rectangle on top, soak with syrup, and spread an even layer of chocolate ganache. Continue: third joconde (soaked) — buttercream; fourth joconde (soaked) — ganache; fifth joconde (soaked) — buttercream; sixth joconde (soaked). Each layer must be level before the next is applied.

Flatten the surface. Run a heated palette knife across the top of the final buttercream layer in a single, steady stroke. The surface must be perfectly flat and horizontal — any undulation will be amplified by the glaze. Refrigerate the assembled cake until every layer is completely set and the structure is rigid to the touch.

This is where the dish lives or dies. Make the chocolate glaze: heat the cream with the glucose until just below a simmer, pour over the chopped couverture, and stir to a smooth, fluid glaze. Allow it to cool until it coats a spoon and flows slowly — it must be fluid enough to self-level but cool enough to set quickly on contact with the cold cake. Remove the cake directly from the refrigerator. Pour the glaze onto the centre of the cold, flat surface in a single, confident pour and tilt the frame — or draw a single pass of a palette knife — to drive it to an even, mirror-flat sheet across the whole surface. Do not work it twice. Any surface irregularity in the assembled cake will read as a permanent ridge in the finished glaze.

Allow the glaze to set completely at cool room temperature, then refrigerate. To portion: heat a long knife blade in hot water and dry it. Trim all four edges in single, clean cuts to expose the full cross-section — six distinct, level layers must be visible. Portion with further single clean strokes of the reheated dry knife, wiping between each cut. The slice is correct when every layer is defined and the total height reads at 2 cm.