I would be curious about this too. I still have one can in my fridge that I brought back on my vacation.
My initial thoughts are all Thomas Fawcett Malts:
OG somewhere around 1.090
FG somewhere around 1.020
ABV: 9.3%
Pearl/Maris Otter Malt (Remainder)
6 - 8% Crystal/Crystal Dark (60-90L)
6 - 8% Dark Chocolate Malt
2 - 4% Roast Barley
0 - 4% Oat Malt (Possibly. Most of the body is from the Conan yeast, but a little oat malt could be a nice touch)
Probably hop extract for bittering. Shooting for 60ish IBU. Little to no flavor/aroma hops. If there are any, it's probably something earthy/floral like EKG/Fuggles/Willamette.
Conan Yeast - this is where most of the body comes from.
Balanced water profile and shooting for a mash PH of around 5.3
The trick is taking this grain bill and getting that chocolate malt flavor to leap out of the glass like The Alchemist beers do. I believe attempts to clone The Alchemist's beers will benefit dramatically from implementing some low oxygen brewing techniques such as a soft boil with a low boil off rate and avoiding herbstoffe at all costs.