Preheat oven to 350 degrees.
Lay the graham crackers in a single layer over the bottom of a baking pan.
Melt the butter and brown sugar together in a saucepan, stirring until melted.
When the mixture just begins to boil, boil for 1 minute.
Remove from the heat and pour evenly over the graham crackers.
Bake for 10 minutes, watching carefully so the mixture does not burn.
Remove from the oven and lay the Hershey bars on top.
Allow the chocolate to soften, then spread evenly over the bars.
Cool completely before cutting into bars.