Black-Bottom Banana Dream Bars

Dream bars are the less-layered ancestor of the seven-layer or magic bar. Here, I riffed on the Coconut Dream Squares from Baker’s Chocolate and Coconut Favorites (1962), replacing the shortbread crust with a chocolate cookie crumb one and adding a bit of salt (like so many of the vintage recipes revamped here, the original called for none), diced banana, just a few mini chocolate chips (because...chocolate), and deeply toasted walnuts for good measur