Neil, best place to find it is to search on my blog... But the salt crust keeps the whole slab done at the same doneness by giving it a bit of a buffer... also *may* keep moisture in. It also adds a nice salty crust that I like a lot.
You just put enough water in it to make a paste, then plaster it on the roast all over the and sides, though I left the ends exposed (the salt makes the ends too salty). Cooked at 225, and I used pecan.
CBJ, some comps, a few awards, Certified Artisan Steak Taster.
XL Big Green Egg, Bubba Keg Convection Grill, Weber Kettle, Charbroil Infrared and mad livefire cooking skillz! :)