Opera is a French café cake of thin layers: almond base, cream and chocolate. Everything depends on precision: thick layers or smeared ganache spoil the cross-section. The usual failures are uneven layers and ganache that has mixed into the cream.
What it is made of
Top to bottom:
- Dark ganache ×2 · 0.5 cm
A thin chocolate cap
- Swiss meringue buttercream ×2 · 1.0 cm
- Almond dacquoise ×3 · 1.2 cm
Three almond layers, two of cream, two of ganache.
An honest note on how this differs from the classic. Classic Opera stands on almond sponge (joconde) soaked in coffee syrup, with coffee buttercream and ganache. In this builder the almond layer is dacquoise, a nut meringue that is crisp outside and chewy inside, with no soaking, and the buttercream is vanilla Swiss. The cake is less coffee and more nutty. You can flavour the buttercream with espresso, but the builder has no coffee layer.
Order of work
Dacquoise (the day before): whites at room temperature, a bowl free of grease, fine sugar added bit by bit until dissolved. Sift almond flour with icing sugar and fold it in with a spatula until even, without beating. Spread thin (about 1 cm) and bake low, around 150 °C, until golden and dry. Cool completely; a warm dacquoise breaks.
Swiss meringue buttercream: warm whites and sugar over a water bath until the sugar dissolves, whip to stiff peaks and let the bowl cool to room temperature. Add the butter in pieces. If it looks curdled, keep whipping: it is usually temporary.
Ganache: pour cream (30% or more) at 80 to 90 °C over chocolate. For the layer between the sponges you want it thicker, around 28 °C; for the cap, fluid, 34 to 36 °C.
Assembly: chill each layer for 10 to 15 minutes before the next, otherwise ganache and cream blend.
- Dacquoise, an even layer of buttercream.
- Dacquoise, a thin layer of ganache.
- Dacquoise, buttercream.
- Chill, then pour the thin ganache over the top.
Slice with a warm dry knife; trim the edges for a sharp cross-section.
Resting: overnight; the layers settle and the dacquoise softens.
What can go wrong
- Layers blended. Not chilled between layers.
- Sticky dacquoise. Sugar not dissolved, or under-dried.
- Buttercream split. Butter and whites at different temperatures.
- Cracked ganache. The cake was too cold or the ganache too thick.
The verdict
Opera is discipline: thin layers and chilling between them. The recipe is simple; the patience is not.