The full fat butter is the perfect vehicle for carrying flavour, and really deepening the taste of your cakes. This cookie butter buttercream is one of my all time faves. The texture of cookie butter is very similar to peanut butter, so you need to whip it right into your buttercream to get a smooth finish.
In a small saucepan over medium heat, bring sugar and cup water to a boil.
While your sugar mixture is heating, place egg whites in the bowl of a standing mixer fitted with the whisk attachment.
When your sugar reaches 230 degrees on the candy thermometer, begin to whip eggs whites at medium-high speed until stiff.
When sugar reaches 240 degrees, remove it from heat immediately, and with the mixer running, add it to your egg whites in a stream and beat on high speed.
Whip your meringue until no heat remains. Place your hands along the sides of the bowl to check.
With the mixer still running, add your butter bit by bit, beating until spreadable, 3 to 5 minutes; then, beat in vanilla.
In your mixer, whip 3 cups of buttercream with cup of cookie butter.