Buttercream (French Crème au Beurre)

French buttercream is a gorgeously smooth, velvety, rich buttercream. Because it's made with an egg-yolk foam (i.e., pâte à bombe), it naturally has a bright yellow colour and a higher fat content than Swiss or Italian buttercream, which are both made with egg whites. This silky-smooth frosting has a mellow sweetness and rich custard flavour that complements coconut cake as readily as it does chocolate. Like Swiss buttercream, it's easy to spread and pipe, so it makes cake-decorating a breeze. It can also be doctored with various extracts, spices, nut butters, or melted chocolate to taste.

1½ cup granulated sugar (250 g)
½ cup water (118 mL)
12 large egg yolks, room temperature
¼ tsp. kosher salt
1 Tbsp. vanilla paste or pure vanilla extract (15 mL)
3 cups (6 sticks) unsalted butter, softened (around 68°F) and cut into small pieces (113 g)

Note: French buttercream requires some attention to detail. It is possible that you might need to make it a few times before you master it. If this is your first time making it, consider making a small batch so you don't risk wasting so many eggs.

Place the sugar and water in a saucepan over medium heat with a candy thermometer. Bring the temperature up to 240°F.

Meanwhile, in the bowl of a stand mixer fit with a whip attachment, whip the egg yolks until light and fluffy. This should take about 3-4 minutes on medium/high speed while the sugar syrup is heating.

With the mixer still running, carefully pour the sugar syrup into the mixing bowl. Make sure you pour it on the edge of the bowl and let it stream down the side into the egg yolks. Do not pour it right into the egg yolks or this could cause them to cook unevenly and leave you with chunks of egg yolks.

Turn the mixer up to high and whip at high speed until the mixing bowl is cool to the touch on the bottom.

Mix in the vanilla and the salt. With the mixer running, add the butter one piece at a time until the piece is absorbed before adding the next.

Use immediately or store covered in the refrigerator for up to 3 days. Re-whip the frosting before using if you stored it.

Makes enough buttercream to frost about 24 cupcakes, or to fill a 4 layer 8" cake or a 3 layer 9 or 10" cake. It is also enough frosting to cover the top of a 9x13" sheet cake. This frosting doesn't work well as the main frosting for a layer cake. It is too soft and unstable.

Cook's Notes:

You want to make sure the butter isn't too warm. A cool room temperature or around 68 F is perfect. This ensures it is soft but not too soft and will not break the buttercream.

There is some debate about whether or not the egg yolks get truly cooked with the sugar syrup in French meringue. That said, if you are concerned about raw egg, make sure you purchase pasteurized eggs.