Opera Cake - French Mocha Buttercream
Prep time
Total time
  • 1½ tablespoons instant coffee
  • 1½ tablespoons cocoa powder
  • 1 tablespoon boiling water
  • 3 large egg yolks, at room temperature
  • 115 grams caster sugar (1/2 cup)
  • 30 grams water (1/8 cup)
  • 225 grams unsalted butter, at room temperature
  • ½ teaspoon vanilla
  1. Combine instant coffee, cocoa powder and boiling water in a small bowl until the coffee and cocoa has dissolved. Set aside.
  2. Fit the whisk attachment onto the mixer. Add the egg yolks into the mixing bowl and beat on medium-high speed until the egg yolks are light and foamy. Stop the mixer and prepare the sugar syrup.
  3. Combine caster sugar and water in a small pot. Let it boil until it reaches 115C / 238F. Immediately remove from heat.
  4. Add the hot sugar syrup gradually to the egg yolks - add a bit of syrup, run the mixer on medium speed, stop the mixer then repeat until all the syrup has been added.
  5. Beat the egg yolk batter on medium speed until the mixture has completely cooled down.
  6. Change the mixer attachment to a paddle attachment. While the mixer is running on medium-low, add in butter gradually. After all the butter has added, whip the mixture on medium-high until the buttercream is smooth, creamy and pale in colour.
  7. Add in the vanilla and coffee-cocoa paste and beat on low until fully incorporated.
Naggy Notes
- If you add the sugar syrup while the mixer is running, the syrup may hit the whisk attachment and splatter onto the sides (the syrup hardens quickly so it cannot be mixed into the egg yolks later) or out (which can be dangerous as the syrup is hot).
- The buttercream may look very loose and watery as you add in the butter, but beating it after all the butter has been added will transform it into a smooth and creamy lusciousness.
Recipe by Foodie Baker at https://www.foodiebaker.com/opera-cake/