***Edit: Whoops, should have been in recipe database. Added here: http://www.homebrewtalk.com/f126/socias-black-chocolate-robust-porter-ag-157403/#post1814558
Here's a Robust Porter (or possibly a RIS) recipe of my own creation that is turning out great. Feel free to use/modify as you see fit.
Socia's Black Chocolate Porter (AG)
Batch size: 5.5 gal
7 lbs Marris Otter
1 lb 5 oz Chocolate Malt
1 lb Crystal 60 Malt
1 Tbsp PH 5.2 Stabilizer (Mash 60 mins)
1.5 oz Fuggles (4.5%) @ 70 mins
1.75 oz Dark Chocolate (Ghirardelli ~70 or 80% cocoa?) @ 50 mins
.5 oz Fuggles (4.5%) @ 10 mins
5 oz Cocoa Powder (Ghirardelli) @ 10 mins
1 lb Lactose @ 10 mins
8 oz Clear Candi Sugar @ 10 mins
8 oz Invert Sugar @ 10 mins
1 Package Nottingham (1L starter)
Single infusion full body batch sparge,
Mash at 157F for an hour or so, using 11.6 qts of water (169F strike temp)
Batch sparge 5.5 gallons of water (168F strike temp)
7 gallon pre-boil yield, estimated pre-boil gravity 1.049 (@ 79% eff)
Primary 22 days @ 65-68F
Notes: I mashed a little lower than I had intended (closer to 153?), and the Invert sugar was a little closer to Amber colored than Clear (home made Candi Sugar using citric acid with table sugar).
I somehow hit 79% efficiency, but I think that's a high estimate (based on previous mashing efficiencies) and the dark chocolate I'm sure had some sugar in it that wasn't accounted for in the calculations. I'd say closer to 70% efficiency and you'd be on track with the OG.
OG was a little high (1.022), but I like my beers sweet.
At almost 3 weeks in the bottle, it's a very chocolately, very smooth, jet black beer. Not too bitter, but not cloyingly sweet either. Good head retention, but only so-so carbonation (I think I used too little priming sugar).