Preheat the oven to 350 degrees Fahrenheit and line a jelly roll pan (10x15 inches) with parchment paper.

Lay the graham cracker sheets on the bottom of the sheet pan in one layer. There is no need to break the crackers but it is ok if they are broken.

Set the pan aside for now.

In a saucepan, over medium high heat, stir the salted butter and dark brown sugar together until the butter has melted and everything is combined.

Bring the sugar mixture to a boil and then reduce to a simmer.

Simmer while stirring continuously for 5-7 minutes or until the mixture has thickened and lightened slightly in color.

Pour the hot mixture over the graham cracker layer and even out with a spatula, if necessary.

Place the pan in the oven to cook for another 5-7 minutes or until the sugar mixture is bubbling evenly all over.

Remove the pan from the oven and immediately sprinkle it with the dark chocolate chips.

Let the pan sit for 5 minutes or until they have melted enough to spread.

Use a spatula to spread the chocolate evenly over the toffee layer.

Top with the Heath toffee bits and then allow the pan to cool to room temperature, about 30 minutes.

Place the toffee in the refrigerator to cool for 1-2 hours or until completely set.

Cut into squares with a knife or pizza cutter and serve.