In a medium-sized metal bowl, whisk together the sugar, egg yolks and water. Set the bowl over a saucepan of simmering water. Do not allow the bottom of the bowl to touch the water. Whisk constantly until the mixture registers 170 degrees on a candy thermometer, about 4 minutes

Remove the bowl from over the water. Using an electric mixer set on high speed, beat the egg mixture until cool and thick, about 5 minutes. Gradually add the butter, about 1 tablespoon at a time, beating until smooth after each addition. Beat in the vanilla exact. If the buttercream appears broken or lumpy, set the bowl back over simmering water for a few seconds, then beat again until smooth.

To store, cover and refrigerate for up to 2 days. Before using, let stand at room temperature until softened. If necessary, rewarm over a sauce pan of simmering water for a few seconds, then heat until smooth.

Makes about 2 1/3 cups

canned sweetened cream of coconut with the sugar and egg yolks. Then add 1 teaspoon imitation coconut extract with the vanilla. Mix 1/2 cup toasted sweetened shredded coconut into the finished buttercream. For coffee flavor: Stir in 2 teaspoons instant expresso powder when the cooked egg mixture is removed from the heat, then beat as directed. For orange flavor: Add 1 tablespoon grated orange zest with the vanilla extract.