Grifola frondosa

Common Name: Hen of the Woods
Description: Fruit body annual; a large clustered mass of flattened, fan- or tongue-shaped caps joined by short stems to a central base; 15-40cm across. Stems laterally attached to rear of caps; white, very tough, many branched from the central core.
Habitat: on ground at base of deciduous trees, especially oak. Frequent. Found widely distributed in eastern North America, rarer elsewhere.
Edible: delicious if the softer caps are well cooked.

Source: Mushrooms of North America by Roger Phillips.