Line a rimmed cookie sheet with foil, butter the foil and place the graham crackers evenly on the sheet.
In a medium-sized, heavy-bottomed pot, melt butter, then add sugar, condensed milk and marshmallows and slowly melt, stirring continually. Pour the mixture evenly over graham crackers and sprinkle chopped peanut caramel clusters on top. Place in a pre-heated 400°F (205°C) oven to bake for 5 to 6 minutes. Using a fork, spread melted clusters around then allow to cool for 10 minutes. Transfer cooled pan to refrigerator for an additional 30 minutes.
Break the candy into chunks and store in a covered airtight container.