Reverse embossing--which may have another name is heating embossing powder until it's molten and stamping an image into it. My cheapo way is to start by inking a piece of chipboard with versamark, add EP and keep adding until it's fairly thick, about 3 layers, then quickly stamp your image.
Ultra Thick Embossing Enamel UTEE is much easier to use, but I didn't have any on hand.
Have fun!