Using a mixer, cream softened butter and vanilla until smooth. Jessica's note: To soften butter, leave on the counter whole for about an hour before use, or 30 minutes if cubed. Always cut your butter in small cubes before putting into mixer, so that the butter will not only blend better, but won't fly everywhere from the mixer trying to cut it!
Add sugar gradually, allowing butter and sugar to cream together before adding more. Jessica's note: Add the three cups in by 1/2 cup increments for a small bowl and 1 cup increments for a bigger one. If you have a splash guard, use it now! Sugar will be flying everywhere. You want to mix your frosting until it is WHITE.Yes, it will look yellow for a while, but after being beat for about 5 minutes it will turn white.This will work perfectly for adding colours so it won't have a yellow tinge.
If you want your frosting a little creamier, add a teaspoon of milk at a time and beat on high until you get the right texture. Jessica's note: a little milk goes a long way. You don't want to end up watering down your frosting so remember, add a little at a time.
Notes
Before I start, this is a basic buttercream frosting. Before you start making your frosting: 1. Make sure you sift your powdered sugar. It tends to harden together in the bag. The easiest way to break it up is to put it in a food processor and blend it. It will be soft, light, and ready to fluffy frosting.During making your frosting: 2. Add any colour you want to add near the middle of the mixing process. That way it won’t streak and your frosting won’t taste like food dye.After you’ve made your frosting: 3. You can put in add-ins such as a teaspoon of most extracts, melted chocolates of all types and other fillings.4. If you realize you want a thicker frosting, add 1/4 more powdered sugar at a time. If you want a thinner frosting, add a tablespoon more at a time.Variations:CHOCOLATE: Add 5 ounces of unsweetened chocolate. STRAWBERRY/RASPBERRY/BLUEBERRY: Add fruit puree to taste, about 3 tablespoons for every 3 cupsLEMON: Eliminate vanilla extract and add 1 teaspoon of pure lemon extract