Preheat oven to 400°F. Line a 13x18 rimmed baking sheet with foil or a silicone liner. If using foil, spray it with nonstick spray. Lay the graham cracker sheets in a single layer, side by side in the pan, breaking pieces as needed to fill the pan.

Place butter and brown sugar in a medium saucepan. Bring the mixture to a boil, and boil for 3 minutes, stirring occasionally. Carefully pour over the graham crackers. Use a rubber spatula to evenly spread the mixture over the graham crackers (work quickly - the toffee will start to firm up).

Place the pan in the oven for 4 minutes. Remove from the oven and place dollops of peanut butter all over the top. Place back in the oven for 1 minute (to melt the peanut butter). Remove from the oven and evenly spread the peanut butter all over the surface. Sprinkle with chocolate chips and place back in the oven for 1 additional minute (to melt the chocolate). Remove from the oven and use an offset spatula to evenly spread the melted chocolate. Don't be too heavy handed, just lightly spread the melted chocolate. Immediately top with chopped peanuts.

Allow to cool to room temperature, then transfer to the refrigerator to firm up completely (at least 2 hours). Once chilled, break the toffee into irregular pieces. I like to store it in the refrigerator.