I'm not vegan, but this is my favorite spot for chocolate-chocolate cupcakes in the Valley. Rather than the dense, fudgy frosting you may find at places like OllieCake/Urban Cookies (which is fine--to each her own!), their chocolate frosting is more of a fluffy-creamy icing, which is way more up my alley. Their chocolate cake is moist and delicious as well.
Treehouse Bakery typically has special cupcake flavors too--I picked up a "spicy hot chocolate" one yesterday which was chocolate cake topped with a spicy cinnamon vanilla frosting. I've also seen cookies & scones but haven't tried them. The staff has also been very friendly every time I've stopped in, so I definitely recommend checking this out if you're in the area.