I'm working up a recipe based on the Deschutes Black Butte Porter clone recipe from The Jamil Show podcast.
Their recipe calls for both English and American chocolate malt. I'm having a hard time finding information about the difference between the two varieties.
The two closest LHBS's to me only carry a single "chocolate malt", without an indication of origin, but given that I live in Seattle I expect it's the American malt. When I asked one of the shopkeepers about the difference he didn't know and couldn't find any relevant information on his bookshelf.
The only source of info on the difference I have is that having plugged the recipe into Hopville, the English chocolate comes up with PPG of 24, and the unmarked (assumed American) chocolate comes up as 34. My assumption, therefore, is that the American version has more starches that will convert and is possibly roasted less than the English version. But I'm just guessing at that, and it doesn't tell me much about the difference anyway.
My plan is to just substitute the American malt for the English malt. It's small enough quantities that it probably won't make a huge difference, but it would still be nice to know more about the English malt and if there is a better substitution.