From a previous NB Forum thread:
I've made the Brew-Haus chokecherry stout a couple times and it's very good. I adopted their method for using chokecherries and developed a Chokecherry Belgian Wit recipe that is also very good according to a number of people...
"Also for my recipe, I've frozen, thawed, then macerated the chokecherries (I do them bit by bit in a food processor, no more than about 15 seconds since you DON'T want to crack the pits since they contain prussic acid, i.e. poison), and stirred that well while pasteurizing them in the wort after the boil, and then strained them out prior to fermenting, rather than tossing them pits and all into the primary fermenter. This makes it easier to rack after primary fermentation. But I had plenty of cc's to work with...
I've tried both removing the stems and not removing the tiny stems and I didn't think the batch with stems came in very noticeably more bitter, although they will for wine or mead."
You can also freeze, thaw and then squish by hand the berries, but I found that the food processor is much quicker and if done right won't crack a single pit, and isn't hard at all to do without cracking pits. I think I got the food processor idea from a blog about making pemmican or mead. PM me if you'd like the recipe. Since they are a strong flavored berry, they are fine for adding pre-ferment. I checked my past batch notes and found that 1.2 pounds of ripe chokecherries per gallon of finished beer is plenty of fruit. The brewer at the time (2006) at Blue Moon Brewing in Bend, OR helped me dial in my recipe. You need to let this beer mature awhile, for the fruit to integrate - it's amazing the transformation it goes through after it's been in the bottle for a couple months. I haven't tried kegging it yet.
The old Brew-Haus (they are/were in Durango, CO) recipe for Rocky Mountain Choke Cherry Stout, no longer available via a Google search (I just tried), they macerated by hand the fruit, pasteurized following the boil at ~160F for 20 minutes, and then dumped pits and all into fermenters for the entire primary.
edited to reduce amount of fruit per batch after checking past batch notes.