Melt the sugar and butter in a heavy bottomed saucepan and bring to a boil over medium heat. Boil for seven minutes stirring constantly. Test in cold water. When the thread cracks in the cold water, pour mixture into a buttered 9" x 9" pan with chopped nuts in the bottom.
Put chocolate chips on top. Cover to contain the heat to melt the chocolate. Spread the melted chocolate and sprinkle with remaining chopped nuts. Let cool. Break into servings.