4-ingredient vanilla frosting, or American buttercream, is made with just butter, icing sugar, vanilla, and cream. Easy, sweet, and perfect for frosting.
Add the butter to a large mixing bowl (or the bowl of your standing mixer). Beat on high speed for 2 minutes, until lighter in colour and fluffy.
Add the sugar, vanilla, and 1 tablespoon of cream. Mix again, starting on low speed and gradually increasing to high, until the frosting is light and smooth, about 3 minutes.
Add the second tablespoon of cream if the buttercream is too stiff.
Rub a little bit of the frosting between your fingers. If it feels at all gritty, keep mixing. It should be very smooth, a light cream colour, and fluffy when it's ready.
Store the buttercream in a sealed container in the refrigerator for up to one week.