From the Clay Teacher - a terrific site full of great projects. They said this could also be done with air dry clay. I like using one earthen color of clay or glaze, but I could see students going crazy with this one with an array of colors.
The Mona Lisa (La Gioconda or La Joconde, or Portrait of Lisa Gherardini, a half-length portrait of a woman by the Italian artist Leonardo da Vinci, art in the world." The painting, is in oil and is now at the Musée du Louvre in Paris.