Wow! Even w/o seeing what you have, you describe a full interior room dividing fireplace that is probably concrete block and brick/stone faced, with a one sided fire chamber in the living room/dining side. It could be openly constructed in a cathedral ceiling enviroment, or in a two story and supports some floor joists above it.
You want to see the fire in the kitchen though, so this guy is going to remove the firebrick, which is the only easy part, as it's just the interior facing that keeps the regular concrete products from disintegrating from the heat, and then he's going to blow a large hole into the block, or if it's a real old house...brick, rocks, mud, trash (even new homes get their share of fill products) clean through to the other side.
I would sincerely look at the date on his insurance policy papers before he even starts the work, cause I picture a scary situation trying to keep an "unknown" construction (the guy cutting into the fireplace did not build it), and very heavy chimney structure above still standing after a bomb goes through the lower middle of it. I would really try to find the person who built it originally, to ask what it's core is made up of, and then find somebody with a lot of previous experience doing what you want. I can't imagine a see through alteration being safe enough without lots of added support modifications not needed before, since it was not originally designed to support a tunnel. Just my humble opinion. Good Luck!

Not a good idea in my opinion. I have been in the construction Industry for about 18 years and started as a Mason. Unless this mason you have is an absolute expert in Masonry, and engineering, I wouldnt even consider it!!

It can be done seeing as it's a ventless fireplace .As long as the mason knows what he's doing which I'm pretty sure he does. Knowing that most masons would not fool around with a fireplace or repair of one without the knowledge. Don't forget he would also be libel if it started a fire, from shody workmanship.At least in Ct.. you are libel.lentels are needed and Im sure he knows that

I'd have a structural engineer look at it first. Even though the mason may be legally liable if you have a problem afterward, as a practical matter, that doesn't mean that you would ever be able to collect any damages from him.