Here’s what it is:

A sizzle platter is an aluminum, or iron, oval-shaped plate that is used either to cook food or to keep cooked food warm. What makes it sizzle is the moisture or juices from the food placed on its hot surface. Sizzle platters are usually heated to a high temperature in restaurants, and the food, usually meat, is either cooked directly on the platter, or cooked partially and finished on the platter. The sizzling comes from the juices mixing with the hot oil on the surface of the platter. If you wish to replicate this at home, heat your platters directly on the stove top and add a couple of teaspoons of oil to them. Cook the beef, chicken, or shrimp on the platter and rush the platter to the table after you turn the meat over to cook the second side. Beef and chicken work best because of their high moisture content.
http://houseandhome.msn.com/Food/Experts/EmerilQA4.aspx

There is a very good picture at this link: http://www.thecruisechef.com/yourkitchen.html

As you can see, it is just a platter (plate), not a “parrilla” or a “plancha.”

I have heard it referred to as a “plato refractario” in Spain—at a steak restaurant, and yes, the steaks sizzled on the plate for quite a while:

En El Schotis dio el salto a gran personaje del comedor, allí aprendió y refinó su estilo culinario incluida la gran invención del plato refractario para las carnes rojas (invención que a este cronista apasiona poco; mejor pidan otro plato normal para trasladar la carne antes de que se quede torrefacta...).
http://www.el-mundo.es/metropoli/2001/582/paginas/comer/poin...

chuletitas de buey (chuletas de carne de buey que se terminan de hacer sobre un plato refractario, deliciosas
http://www.infonegocio.com/atlanticls/Noticias/noticias_octu...

Hope it helps.


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Note added at 14 hrs 58 mins (2003-07-04 10:16:01 GMT)
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The food is actually served (brought to the table) on the sizzle platter, so it is really still cooking when it\'s brought to you (at least in the case of steak, which is the one I have personal experience with).