preheat oven to 350ºF rack in middle position

line a 10 x 15" cookie sheet with heavy foil, covering up the side edges also,(jelly roll pan works great here), spray the foil real well getting the sides also( you want to be able to peel this off later after the candy hardens)

line the bottom of pan with a single layer of graham crackers, cover the whole bottom, break up the crakers if you need to, to be able to cover the complete bottom of the pan

combine the butter and brown sugar in a saucepan over med high heat, bring to a boil stirring constantly, boil for exactly 5 minutes, stirring it constantly

then pout over the graham crackers as evenly as you can, slide pan into the oven and bake for 10 minutes , remove pan from oven, and sprinkle the chocolate chips all over the top, give the chips a minute or two to melt, and then spread them out as evenly as possible, put the pan in the refrigerator to chill,

when pan has chilled, peel foil away from bottom and sides, then break into random size pieces