An unusual, slender black bean from the bean-growing traditions of Oaxaca, Mexico. The name negro delgado refers to its narrow, elongated shape, noticeably different from the rounder black turtle beans familiar in American markets. Its appeal is as much in the cooking liquid as in the bean itself: a dark, deeply flavored broth and small beans that become tender without losing their identity. Cook with onion, garlic and epazote, and serve with warm tortillas. A beautiful example of the extraordinary regional diversity of Mexican beans.