01 -
Heat your oven to 350°F. Use non-stick spray on a 9x13 pan or line it with parchment to make lifting the bars out easier.
02 -
Combine the graham cracker crumbs and melted butter in a medium bowl. Spread this into the pan and press flat to form the base layer.
03 -
Drizzle the sweetened condensed milk all over the crust, making sure to coat the entire base evenly.
04 -
Spread half the marshmallows (1 cup), all the chocolate chips, and the graham cracker chunks on top of the condensed milk layer.
05 -
Put the pan in the oven and bake for about 15 minutes, or until the marshmallows start puffing and golden edges form.
06 -
Take the pan out of the oven and sprinkle the rest of the marshmallows (1 cup) across the entire top to cover any bare spots.
07 -
Place the pan back in the oven for another 10-15 minutes to toast the marshmallows on top until golden brown.
08 -
Pull the pan from the oven and scatter the broken chocolate bar pieces on top. Let them melt slightly from the heat.
09 -
Let the bars cool on a rack for 15 minutes. For neat slices, leave them to cool completely, but they're great gooey too.