A method of shaping an aspherical optical element, such as a composite mirror element, the method comprising the following steps: fastening, preferably by adhesive, an optical element blank, presenting an optical surface that is to be shaped, to the inside of a ring, the optical surface of the blank projecting beyond an edge of said ring; applying forces and moments to the perimeter of the ring in such a manner as to deform it in controlled manner, thereby also deforming the optical surface of the blank fastened to its inside; shaping said deformed optical surface by abrasion so as to restore it to a shape that is spherical or planar; and extracting the blank from the ring so as to release the stresses deforming said shaped optical surface, thereby enabling it to acquire the desired aspherical shape.