Althaea officinalis - L.
"The root is used as a vegetable ... and dried then ground into a powder, made into a paste and roasted to make the sweet 'marshmallow'. The root contains about 37% starch, 11% mucilage, 11% pectin. The water left over from cooking any part of the plant can be used as an egg-white substitute in making meringues etc. The water from the root is the most effective, it is concentrated by boiling until it has a similar consistency to egg white."