Why brown the butter?
Browning butter toasts its milk solids, which gives these cookies a deep, nutty, almost toffee-like flavor that plain melted butter can't match. It takes about five minutes and is the biggest flavor upgrade you can make to a chocolate chip cookie.
Mini marshmallows go in two ways: folded into the dough, then pressed on top right before baking so they toast golden in the oven.
