At first glance, it looks like meringue buttercream or whipped white chocolate ganache, maybe even cream cheese frosting - but it's not. I was experimenting in the kitchen (as always) and made this by accident. It was one of those days when my multitasking got the best of me and for a moment, I forgot what I was doing (oh yeah, I'm not perfect, what's new?). I measured the wrong amount of milk or butter or something (I can't even remember anymore) and voila! I made a frosting that looked smooth like meringue buttercream, but it was made with butter, powdered sugar, vanilla extract and milk, just like classic buttercream. It was not as sweet as classic buttercream but the mouthfeel was almost as silky as meringue buttercream.
After making this "hybrid" several more times, I decided to add whipping cream to lighten it up a bit. I've used this to cover cakes, pipe borders and scrollwork and make swirls on top of cupcakes. I LOVE meringue buttercream (Swiss method because it's the easiest to make and doesn't involve hot sugar), but it's nice to have this as an alternative when I need something that doesn't involve cooking egg whites.
Hybrid Buttercream Frosting
Allergy Note: contains dairy
1 cup butter, softened to room temperature
2 cups powdered sugar
2 tsp vanilla extract
1/2 cup warm milk
Beat the butter, powdered sugar and vanilla extract at low speed until combined. Slowly add the warm milk. It will separate at first, but don't worry - give it a few minutes and it will start coming back together. Increase the speed a little to whip it up a bit. Slowly pour in the cold whipping cream. Whip for a few more minutes and it should start to look smooth. It may curdle or separate again when you pour in the whipping cream, but give it some time and it will smooth out again.
Here are some cakes I've made where I used this hybrid buttercream.