Place sugar and butter in a quart saucepan with the water. Heat until butter has melted, stirring constantly. Cook and stir constantly for 10 minutes or until mixture turns amber color. At this point, the temperature is 320 degrees.
Add vanilla. Pour quickly into a thin layer in a greased 9x12 inch pan. Lay broken chocolate candy bars over the hot candy layer. Spread evenly over toffee and sprinkle with the chopped pecans. When cool, break toffee into pieces.
