Learn how to make the best French buttercream recipe using egg yolks, sugar syrup and butter. This frosting holds its shape very well and it's very smooth!
Place the egg yolks into a stand mixer bowl and whisk on medium-high speed for a few minutes until thick and pale.
Meanwhile, combine the water and sugar in small saucepan. Heat the sugar, not stirring, over medium-high heat until the temperature reaches 238F/115C, about 5 minutes. Keep the mixer running on medium speed and pour the hot syrup in a slow and steady stream into the egg yolks.
Once all the sugar syrup has been added, turn the mixer up to high speed and whisk for 5 to 7 minutes, until mixture is thick and pale in color. It also needs to be just lukewarm to touch. Begin adding the butter, 1 to 2 tablespoons at a time, mixing for about 15 to 20 seconds after each addition. Scrape down the sides of the mixing bowl often to get all the butter mixed in well.
When you start adding the butter, the frosting is going to look like it's separated and ruined. Don't worry! The buttercream will start to thicken as more butter is added and it will come together!
After adding the butter, add the melted chocolate, salt and coffee extract. Mix again for a few minutes until a uniform and fluffy frosting forms.