Preheat the oven to 350° F. Line a 9×9 inch baking dish with parchment paper.
Place the butter in the prepared pan. Melt in the oven for about 5 minutes.
Over the butter, layer the oats, coconut, 1 cup chocolate chips, cashews, and 1 more cup of chocolate chips.
If desired, arrange a few pretzels on top.
Evenly pour over the condensed milk.
Bake for 30 minutes.
Cool completely, then cut into bars.
