Heat the sugar, syrup, water, and pecans in a heavy saucepan until the sugar is disolved. Bring the mixture to the boil, stirring occasionally, until it reaches the soft ball stage (240F). Remove the saucepan from the heat and add butter and vanilla.
Allow candy to cool. Whip until the mixture gradually changes to an opaque color and becomes creamy. Drop by tablespoonfuls onto a buttered cookie sheet and allow to harden. Makes two dozen. From Nathalie Dupree's New Southern Cooking Nathalie Dupree writes, "Pralines are traditionally given as Christmas gifts. Their sweetness will linger in your mouth long after the candy is gone."