I got it from here: http://www.foodnetwork.com/recipes/gale-gand/quick-vanilla-buttercream-frosting-recipe/index.html
I love this frosting. Fast, easy and delicious!
1 cup butter
1 teaspoon vanilla extract
1 to 2 tablespoons whipping cream
Use a hand held or standing mixer fitted with a whisk. Mix together sugar and butter. Mix on low speed until well blended and then increase speed to medium and beat for another 3 minutes.
Add vanilla and cream and continue to beat on medium speed for 1 minute more, adding more cream if needed for spreading consistency.