Best Buttercream Frosting

I'm gearing up for a birthday bash over the weekend, so I'll be posting some of the recipes we use as I make them. This recipe comes from my good buddy, Alton Brown, and really, it is the creamiest, yummiest frosting I've found. Alton says box cake mixes are superior to what most home cooks can produce because of many ingredients we can't get our hands on readily; but, if you use one, make sure to top it with homemade frosting!
*6 oz. butter, room temperature
*2 oz. shortening (1/4 c.)
*1 egg, room temperature
*1 lb. powdered sugar
*1 tsp. vanilla

In a mixer with a paddle attachment, cream together butter and shortening on high speed until light and fluffy (about 3-4 minutes). Add egg and mix on high until thoroughly mixed (3-4 min.). (Alton suggests we make peace with the egg and realize that although eggs could potentially be dangerous, if they are clean and come from a reputable grower, you're going to be fine. I have a doctor friend who backs this up...so I'm eating it and feeding it to my 1-yr-old as well!) While the egg is mixing in, walk away or don't look into the mixer because it looks gross and slimy, but give it a couple minutes. Work powdered sugar into frosting 1/2 c. at a time until sturdy enough to frost. Add vanilla and mix again. This makes about 4 cups and will frost the standard 24 cupcakes, 9x13, or 9" round.