1. Heat the rum, sugar and corn syrup in a saucepan over low ehat, stirring gently until the sugar dissolves. Wash down the sides of the pan with a pastry brush dipped in ice water. Clip a candy thermometer to the side of the saucepan, raise the heat to medium and boil without stitting until the syrup registers 240F (soft ball stage). Remove the syrup from the heat and let it cool slightly while you complete step 2. 2. In a large bowl, beat the egg yolks and vanilla until the mixture is pale and thick and falls in a ribbon when you lift the beaters. 3. Add the hot syrup to the yolks by pouring it down the side of the bowl a little at a time, beating it in after each addition. (Pouring down the side of the bowl keeps the syrup from falling directly on the beaters and forming spun-sugar threads.) Let the yolk mixture cool. 4. Add the butter one Tbsp at a time, beating well after after each addition. The frosting should be thick and perfectly smooth. Use this buttercream as soon as possible, or refrigerate it for up to three days if necessary. When you take it out of the refrigerator, let it come to room temperature and then beat until smooth and spreadable again. Posted to EAT-L Digest by Sean Coate on Nov 23, 1997