Good treatment of this mushroom in Kuo’s “Morels” book. Cap is tightly attached to the stipe; when sliced in half, resembles a stalk of broccoli! As Darv points out, esculenta has a tan or pinkish stipe, never pure white (atho the white stipe of caroliniana can bruise brown).
Gyromitra caroliniana appears to lack detectable amounts of hydrazines and MAY be a safe edible. This is not the case for the seriously toxic G. esculenta.
Nancy Smith Weber, in “A Morel Hunter’s Companion,” reports that Ken Cochran, former NAMA toxicology chair, tested G. caroliniana for hydrazines (MMH) and found them lacking. Whether this is true for all members of this species in all areas is unknown, as is the number of specimens that were tested.