One definition of Intaglio is "ornamentation with a figure or design sunk below the surface". This technique has been called Intaglio and the Extra Thick (or UTEE) Embossing Technique and probably several other names as well. I've also seen this technique done with regular embossing powders using more layers of embossing.
Start with a thick card stock, you can use plain or colored card stock or ink the card stock. Since I am experimenting, I pulled out a previous done background that I didn't like at the time. Cover the surface with VersaMark ink (it helps if you re-ink the pad before doing this technique). Coat the surface with embossing enamel and heat set. I've seen people add extra embossing enamel while the previous layer is still hot and heat again, but I find the layers work better if I coat the layers with VersaMark ink before adding the next layer with embossing enamel and then heat setting. I did 4 layers of VersaMark-embossing enamel-heat set.