Ombre Swiss Meringue Buttercream
Buttercream will keep, covered and refrigerated, for up to 3 days. Bring to room temperature, then beat on low speed before using.
For this ombre buttercream: 1) Add softened butter to the whipped meringue 1 piece at a time. This will initially deflate the mixture to the point of appearing soupy, which is normal. Continue to beat until the buttercream is smooth and glossy. It may appear curdled along the way; keep beating. 2) Starting at 1 corner of frosted cake, pipe plain buttercream into several rosettes. Squeeze buttercream from pastry bag into a bowl, and add coloring to attain desired shade. Resume piping, and repeat as desired, gradually creating an ombre effect.