one of the most underutilized parts of the banana plant as an edible vegetable is its stem, or rather the core of the stem. Its only recently that these specimens have begun appearing in Indian grocery stores and even those are not very good specimens unless you know how to select them.
The stem core has long been a cherished ingredient in traditional home cooking in South India. It has a crisp texture reminescent of Jicama and a delicate vegetal flavor that belies the sturdiness of the ingredient. Not sure how valid the statement is, but the belief is that it helps dissolve kidney stones. , Irrespective, due to the near neutral flavor of the banana stem, it tends to absorb and showcase flavors quite well. The prepping is a tedious task and I'm just going to provide a link to an old blog post of mine that gives you the details ( http://www.panfusine.com/2013/09/somewhat-rare-treats-banana-stem-stir.html )
As of the present, I've seen banana stems sold only in Indian grocery stores in New Jersey. Look for stems that have a big core. ~ 2 inches in diameter. It is this dense center that will be used and the surrounding sheath which is extremely fibrous (in fact they make ropes with the outer part of the stem) is inedible and discarded.