Black Beans! But never be afraid to mix, match, and substitute. As far as additives, I'll leave that to others. For me, as long as it's vegetarian.. anything goes.

black beans are very good and rich but if you're looking for that original taste and look go for Peruvian beans they are way better than pintos, less gassy and have a richer flavor. All you need is a head of garlic, one full onion some salt, and you can even put a couple serranos when cooking them with boiling water and your good to go.

Have not located Peruvian beans. Will keep looking.