Recipe Question - Chocolate Imperial Stout

[Wutz]

*cross-posted in BeerAdvocate's homebrew section so, if you saw it there (and you are the one guy who replied) you can ignore this; I'm hunting for opinions.

First of all, my apologies. I try not to ask recipe questions but I'm in no-man's land on this one. I typically brew bitters, browns, wheats, and every now-and-then a 5.5% IPA so this is way out of my comfort zone.

So, here's my question with a lengthy bit of preamble/pre-thinking:

I'm planning to brew a 6-gallon batch of Imperial Stout with an addition of up to 4oz of TCHO Cocoa Nibs.

I'm scheming on the recipe formulation and, knowing that the nibs will impart a bitterness of their own, I can't decide on an appropriate IBU level nor on the amount of crystal/caramel malt. Another thing to consider is the perception of bitterness imparted by the roasted grains. Those things, in conjunction with mash temp., are going to give me a whole host of sweetness, caramel, and bitterness levels to keep in mind.

I don't think I'd mind if the beer came out a little sweet (to emphasize an almost "chocolate bar" character) but I don't know how much bitterness the nibs will contribute. This will be the first imperial stout I've brewed so, similarly, I'm not sure how much roasted grain to throw at it to get it to balanced Imperial Stout land.

So, without further adieu, here's the recipe I've schemed up so far:

13lbs 2-row
2lbs Munich 10
1.25 lbs Flaked Oats
1lb Cane Sugar
0.75lb Crystal 120
0.75lb Chocolate Malt (350ºL)
0.75lb Roasted Barley
0.5lb Special B
0.25lb Crystal 60

1oz Galena (13%AA) 60 mins
2oz Cascade (5.5%AA) 10 mins
1oz Willamette 0 mins
1oz Centennial 0 mins

Plenty of Wyeast 1028 London Ale

Mash low, maybe 148-150
Fement near 65ºF
After a two-week fermentation, drop the 4 oz of cocoa nibs in and store for 1-to-3 months depending on taste.

Predicted:
Efficiency 65% (because this is the first big beer I've brewed, I'm unsure of my efficiency, I typically get low 70s, though)
OG: 1.082
FG: 1.023-ish
IBU: 71

So, friends, looking at that recipe, that projected process, and those predicted numbers - do you have any suggestions or thoughts?

Thanks in advance to anyone who bothers to reply.

[pythoner]

I have used coco nibs and they do inpart a little bit of bitterness. I do have to say that took a foreign extra stout that had 8 oz coco powder and it was just missing something. I later tossed in two ounces of oak cubes and on day eleven everything came together and the beer went from ok to amazing.

EDIT Also the oak makes it taste more like chocolate instead of coco

[siwelwerd]

After a two-week fermentation, drop the 4 oz of cocoa nibs in and store for 1-to-3 months depending on taste.

Not sure you want to leave the nibs in there long term. I did a Chocolate Coffee Porter with nibs, dropped 4 oz in the carboy, waited until I had the chocolate where I wanted (10 or 11 days for me), and racked off of them into the keg. I suspect you might need longer with a big roasty stout, but I would still suggest tasting it and planning to remove it from the nibs.

[speed]

hey wutz i heard you had a big train wreck in town whats up with that?

[Wutz]

hey wutz i heard you had a big train wreck in town whats up with that?

I'm not sure if the train wreck you're talking about is my brewing or this:

http://www.bismarcktribune.com/news/loc ... 03286.html

...but both are messes, though.

I don't actually know anything about the train wreck other than my wife had a pretty difficult time getting to work because of it. How did you hear about it down in Nebraskaville?

Not sure you want to leave the nibs in there long term. I did a Chocolate Coffee Porter with nibs, dropped 4 oz in the carboy, waited until I had the chocolate where I wanted (10 or 11 days for me), and racked off of them into the keg. I suspect you might need longer with a big roasty stout, but I would still suggest tasting it and planning to remove it from the nibs.

I just assumed it would be a long time, but I'll definitely be tasting to determine contact time instead of just waiting an arbitrary length of time. But I'm definitely glad you've successfully used these things before. How much bitterness did you end up picking up from them? Was it a IBU-style bitterness or was it a roasted barley-style bitterness?

[siwelwerd]

I don't think I got much bitterness at all out of them. It may be time dependent--the longer you leave them, the more you may get. I think your roasted malt will contribute more perceived bitterness than the chocolate.