1. Mix yolks, confectioners’ sugar, and margarine on high speed for five minutes.
2. In small saucepan over medium-high heat, dissolve sugar in water, stirring constantly until the mixture has reduced by half. It should be lightish brown in color.
3. Pour hot sugar into yolk mixture and mix for one minute. Cool.
4. Spread onto top layer of cake.
5. Cut into two- by two-inch squares to serve.