Jeff's suggestion is pretty good, but I think his recipe will result in a slightly higher ABV and slightly lower IBU than the brew you are trying to clone. I would try this:
Method: Extract
Style: Brown Porter
Boil Time: 60 min
Batch Size: 5 gallons
Boil Size: 3 gallons
Efficiency: 75%
Original Gravity: 1.072
Final Gravity: 1.020
ABV (standard): 6.83%
IBU (tinseth): 34.37
SRM (morey): 32.63
Fermentables
Amount Fermentable PPG °L Bill %
6.5 lb Dry Malt Extract - Light 42 4 68.4%
1 lb Dry Malt Extract - Wheat 42 3 10.5%
Steeping Grains
Amount Fermentable PPG °L Bill %
1 lb Chocolate 29 350 10.5%
0.5 lb Munich - Dark 20L 33 20 5.3%
0.5 lb Caramel / Crystal 120L 33 120 5.3%
Hops
Amount Variety Time AA Type
1 oz Magnum 60 min 15 Pellet
1 oz Goldings 10 min 4.5 Pellet
0.5 oz Goldings 5 min 4.5 Pellet
Yeast
Fermentis / Safale - Safale - English Ale Yeast S-04
This recipe has a slightly smaller grain bill (less extract) and slightly more hops than the one Jeff suggested. The hops addition schedule was also changed slightly. I think it will get you a little closer to the beer you are trying to clone, but I think either his recipe or this one would make excellent beer.
I calculated this recipe using a 3 gallon partial boil since I did not know the size of your brew kettle. If your pot is able to boil more than 3 gallons, I can recalculate the IBUs for the new boil volume and see if we need to modify the hops to keep the bitterness where you want it.
