Preheat the oven to 375F (191C, gas mark 5). While the oven is preheating, you will put the ingredients together.
Melt one stick of butter and pour it in your 9"X13" pan. Make sure the butter touches every part of the bottom of the pan and try to spread it evenly.
Spread one cup of graham cracker crumbs evenly over the butter. Use more crumbs if you need them for an even layer.
Sprinkle one cup of chocolate chips them all over the graham cracker crumbs crumbs. They don't have to be even, but try to cover as much as possible.
Sprinkle the butterscotch chips over and between the chocolate chips.
Sprinkle one cup of chopped walnuts and over the chocolate and butterscotch chips.
When you are sprinkling the ingredients over one another, they don't need to cover the entire pan; just try to distribute them evenly across the pan.
Cover the entire pan with 1 cup of the shredded coconut. If you need more, feel free to add more, but keep it a fairly thin layer.
Spread one cup of marshmallows in the next layer. The pan doesn't need to be covered, but there should be a good amount of marshmallows on the pan. If you need to add more feel free to do so.
Pour the can of sweetened, condensed milk over the entire thing and let it run through all the layers.
Put the pan in the oven and let it cook. It should take approximately 10-15 minutes, but some ovens are different, so keep an eye on it. Once the sweetened, condensed milk turns a golden brown it is done.