In a bowl combine: one box of confectioners' sugar, one stick of unsalted butter, one teaspoon of pure vanilla extract, and 1/4 cup of milk or light cream and beat for a while. Really whip it, don't be afraid to get in there. I occasionally add food coloring and sometimes substitute pure almond extract for vanilla.
If you do choose to add pure almond extract instead of vanilla, you're on your own. I don't know the measurement for it, but I do know it's less than the amount of vanilla you would add.