Basic Italian Buttercream

Place egg whites in the bowl of a mixer fitted with the whisk attachment. Set aside.

Attach a candy thermometer to the side of a saucepan. Add sugar, corn syrup, and water; bring to a boil. Brush the sides of the pan with a clean pastry brush (free from fat and oil) during the boiling process.

When the sugar syrup reaches 110°C or 230°F, turn on your mixer and start whipping the egg whites at high speed. Whip until they form soft peaks. Continue boiling the syrup until it reaches 115°C or 240°F (soft-ball stage).

Remove saucepan from heat. Lower mixer speed to medium. Pour syrup  into egg whites in a thin, steady stream between the wire whisk and the side of the bowl. Be careful-if the syrup hits the whisk, it will splatter and create lumps.

Increase the speed of the mixer to high. Continue whipping the meringue until it has cooled completely and has formed stiff peaks.

When the meringue has been whipped to stiff peaks and is lukewarm, change the wire whisk to the paddle attachment. Lower mixer speed to medium and gradually add butter and vanilla extract. The butter must not be too cold when added because this will cause the mixture to break or split. If this happens, beat for another five minutes until smooth and fully incorporated.

Transfer to a clean container, cover with plastic wrap, and store in the refrigerator until ready to use.