Butter Cream Icing
3-1/2 cups sugar
13 large egg whites
3 pounds (12 sticks) unsalted butter, at room temperature, cut into half sticks
6 tablespoons clear vanilla extract
In a medium saucepan, combine the sugar and 3/4 cup water, mixing with a wooden spoon until the sugar is mostly dissolved. Place the pan on the stove, and use a clean pastry brush to paint the area just above the water line with water. Turn the burner on to medium and heat, watching the sugar mixture to be sure it does not carmelize or burn. Lay a candy thermometer in the pan and simmer the sugar-water mixture without stirring until the thermometer reaches 240 degrees F (soft-ball state); this will take about 5 to 7 minutes.
As the sugar nears the required temperature, place the egg whites in the large bowl of an electric mixer. Using the wire whisk attachment, beat the egg whites at medium speed until they turn from opaque to white and begin to hold soft peaks. They should be at least double in volume in about 3 to 5 minutes. Do not overbeat.
Turn the mixer on high and very carefully and slowly pour the hot sugar mixture in a very thin stream near the edge of the bowl and into the stiffly beaten egg whites. Beat for 20 to 35 minutes on medium to high speed. The egg whites will lose some of their volume and the mixture should resemble a very thick meringue. The outside of the bowl should be moderately warm to touch. At this point, reduce the speed to medium or low and add the room temperature butter pieces, one at a time. The mixture will break and begin to look like cottage cheese, but don't worry. Keep the mixer running, continue adding butter, and let the mixer whip the buttercream until it begins to get smooth once again; this could take up to 10 minutes. Once the mixture is smooth, add the vanilla and beat for five minutes more. The buttercream is now ready to be colored or chilled. (If the buttercream is too soft, chill for 10 minutes and then whip again. If this doesn't work, cream 4 tablespoons of chilled butter, and then gently whip the creamed butter into the buttercream, 1 tablespoon at a time. Beat until the buttercream is smooth and there are no lumps.)