Young's Double Chocolate

Someone needs to explain to me how Young's has such a clean and un-bitter finish. I'm drinking one right now, and the bitterness just doesn't stab you at all like some other stouts. Any suggestions re: how to approximate that in a homebrew, preferable via extract? What proportion of special grains? I'm not necessarily searching to duplicate a Young's, just trying to get that un-bitter, smooth finish.

EDIT: I'm drinking an Elysian Drangonstooth now, and it has a similar finish. Slightly more bitter, but for the most part very smooth and fantastic. Is roasted barley the evil culprit? And if so, how does one part with it? I'm sure it's not as simple as substituting chocolate malt in equal quantity...

Austin homebrew's "double chocolate stout" is supposed to be pretty close to Young's, based on reviews around here and on their site.

I'd start there.

Keep the heavy, dark, roasted malts to a minimum, mash high, keep the IBUs low, and consider back-sweetening with lactose.