In an iron skillet, cook sugar and butter to "hard cracked" stage. (I always use a candy thermometer) Stir constantly! The color will change to a butterscotch color near the end.
Immediately spread onto a large butter cookie sheet. Top with Hershey Bars and spread until melted over the top. Sprinkle with chopped pecans and let completely cool. I usually put it in the frig until it sets up.
Break into pieces and keep in a covered tin in the refrigerator until ready to serve.