I followed the recipe pretty much to a T (I think it tastes great with butternut squash) but I might even add more onions next time. The caramelization makes them deliciously sweet but they break down in the process, so a bit more wouldn't have hurt. It's the first time I've truly caramelized onions (it took about 30 minutes overall) and I used apple cider vinegar and maple syrup a friend brought from Canada.
As Bittman mentions, the mint on top takes the dish to another level. Somehow, the sweet and tangy onions, the smooth squash, and creamy ricotta all come together with the herb.
Caramelizing onions (patience required!)