The pasilla chilli also known as the chilli negro is the dried form of the Mexican chilaca chilli pepper, a long and narrow member of the species Capsicum annuum. It's so named for its dark, wrinkled skin and in Mexican is pronounced pah-SEE-yah (literally "little raisin"), it is of a mild to medium-hot, rich-flavoured chilli. As dried, it is generally 6 to 8 in (15 to 20 cm) long and 1.0 to 1.5 in (2.5 to 4 cm) in diameter. 

The fresh narrow Mexican chilaca can measure up to 9.0 in (22 cm) long and often has quite a  twisted shape, which is seldom apparent after drying. It turns from dark green to dark brown when fully mature.

Pasilla are used especially in Mexican sauces.and are often combined with fruits and are excellent served with duck, lamb, seafood, garlic, mushrooms, fennel, honey, or oregano.
These chilli's are sold whole or powdered in Mexico, the United States, and also the United Kingdom