I've made balsamic brown butter many times before (it's one of my favorite "sauces" for store-bought ravioli) but I'd never thought to roast mushrooms or vegetables in it until today. My roasting game for the fall just got a whole lot better! : )
To make this, I browned 1/2 stick of salted butter, then added 1 tablespoon of balsamic and a little honey off the heat. I tossed about 3/4 pound of cremini mushrooms, a sweet onion, lots of thyme, and salt and pepper together, then roasted at 425 for about 40 minutes.