I've done a good amount of solid headpieces, and I dun think the fabric cowl will really get the sharp, defined look the Bat tends to rock... what I would recommend is my method, get some aluminum wire mesh from a craft store, fairly reasonable for a roll, and use it to create the shape of the cowl. I'm a huge fan of Crayola's Model Magic, used it for my revamped Witch King, Mumm-ra, and my Rose mask, and it's rather easy to work with, no mess, crumbling, and it air dries into a really dense foam-type material. It does shrink a bit when it dries, so if you're building over a wire frame be generous. The shrinkage shouldn't be a major problem.
If ye still wanted to do a fabric version, make a headband or something with wire-model magic pointy ears on it and have them poke out. Just my two cents X3
Confirmed Otakon cosplays:
Farfarello - Weiß Kreuz
Los Lobos Starrk - Bleach
Bandit Keith - YuGiOh
Witch King of Angmar - Lord of the Rings
Kunzite - Sailor Moon