Melt butter in heavy saucepan. Add sugar, water and corn syrup and cook
over medium heat, stirring until sugar dissolves. Cook, without stirring, to
300 degrees F on candy thermometer or hard crack stage.
Remove from heat.
Quickly stir in 1 1/2 cups nuts and pour onto lightly greased cookie sheet.
Melt chocolate over low heat. Spread over cooled toffee.