What he said. I'd guess that, being laminated, it has a poly-type finish. Two things I have used that won't harm most finishes (bets are off if the finish is already damaged from heat) are a strong Murphy's Oil Soap solution and, if that doesn't work, try "Goof-Off". Once you get the soot and grunge off you'll have to decide if the whole needs stripping and refinishing, or just steel wool and a few fresh coats.
I'd try contacting the manufacturer to see what they use. You don't want to slap an incompatable finish over what is already there.