Pasilla refers to more than one variety of chile in the species Capsicum annuum

Capsicum annuum

Capsicum annuum is a domesticated species of the plant genus Capsicum native to southern North America and northern South America. The three species C. annuum, C. frutescens and C. chinense all evolved from a single common ancestor located somewhere in the northwest Brazil - Colombia area...

. A true pasilla is the dried form of the long and narrow chilaca pepper. However, in the United States producers and grocers often incorrectly use 'pasilla' to describe the poblano

Poblano

The poblano is a mild chili pepper originating in the State of Puebla, Mexico. Dried, it is called a chile ancho . The ripened red poblano is significantly hotter and more flavorful than the less ripe, green poblano. While poblanos tend to have a mild flavor, occasionally and unpredictably, they...

, a different, wider variety of pepper whose dried form is called an ancho.

Pasillas are used especially in sauce

Sauce

In cooking, a sauce is liquid, creaming or semi-solid food served on or used in preparing other foods. Sauces are not normally consumed by themselves; they add flavor, moisture, and visual appeal to another dish. Sauce is a French word taken from the Latin salsus, meaning salted...

s. They are sold whole or powdered in Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

, the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, and the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

.

Chile negro or chilaca

The pasilla chile or chile negro is the dried form of a variety of Capsicum annuum

Capsicum annuum

Capsicum annuum is a domesticated species of the plant genus Capsicum native to southern North America and northern South America. The three species C. annuum, C. frutescens and C. chinense all evolved from a single common ancestor located somewhere in the northwest Brazil - Colombia area...

named for its dark, wrinkled skin. In its fresh form, it is called the chilaca. It is a mild to medium-hot, rich-flavored chile. It is generally 6 to 8 inches (15 to 20 cm) long and 1 to 1.5 inches (2.5 to 4 cm) in diameter. The fresh narrow chilaca can measure up to 9 inches (22 cm) long and often has a twisted shape, which is seldom apparent after drying. It turns from dark green to dark brown when fully mature.

Pasilla de Oaxaca is a variety of smoked pasilla chile from Oaxaca used in mole negro

Mole (sauce)

Mole is the generic name for a number of sauces used in Mexican cuisine, as well as for dishes based on these sauces...

.

Pasilla peppers are often combined with fruits and are excellent served with duck, seafood, lamb, mushrooms, garlic, fennel, honey, or oregano.