A good plasterer can do it, although they will need at least two coats. Not a DIY project as it's very hard to end up with a smooth level surface - anything less than that will look bad when the light hits it. Drywall attached with the proper construction adhesive is the simplest and cheapest way to do it. If you use 1/2" drywall and adhesive it won't stick out much more than a few coats of plaster would.

Actually, I have done some plastering. The walls have some texture, skip troweled, and since I pay extreme attention to detail, I will probably try it my self...and the friend we bought the mantel is a contractor and has give us some helpful hints...