This grower is fairly sure of this plant identification.
white flowered form
Francoa genus (Bridal wreath). There are about 5 species of evergreen perennials. They will form a basal rosette of lance-shaped to obovate, lobed leaves. The petalled flowers are cross-shaped and will bloom in white, pink or red. they are frost hardy and will need full sun and fertile, well drained soil. You can propagate by seeds or division in the spring.