Chiaroscuro lighting is the use of stark and dramatic light set against a dark background. It is considered low key lighting as the overall effect and composition has more dark areas than light. The term also describes the art technique in showing/applying the contrast and it's transitions between the light and dark areas of some part of the main element of your image.
Here we are employing that technique with a "MODIFIED" Rembrandt set up. Rembrandt lighting, typically, is the key light illuminating the "short" side of the face while having the nose cast a shadow onto the broadside of the face and creating a "light" triangle illuminating the eye and a triangular area beneath it. The fill side can be another, lower brightness level, light or bounce card kicking light into the shadowed area of the broadside of the face. This image is the reverse of that and the MODIFICATION will be described in the steps bellow.