Russian Imperial Stout

The extreme version of stout. Imperial Stout is a category that can be pushed as far as the yeast, wallet, and equipment can allow. It is a little tougher to get a higher gravity with an Imperial Stout than a Barley Wine as there are a couple of pounds of specialty grains to add, which if maximum is desired, reduces base malt accordingly and thusly alcohol.
First, this is a beer that can be made with extract added after the mash process is complete to boost the OG without detriment.
Second, generous amounts of roasted barley will contribute to bitterness and flavor, reducing the need for huge hop amounts (though huge amounts can be used).
Thirdly, the brewer must determine what he or she can get out of their system as far as an OG goes. I use a double mash, boiling first runnings while the second mash is being done. This adds some caramelization to the wort and raises the gravity a bit. Doing one full mash for a 5 gallon yield on a 10 gallon or more system will also work. The recipe below follows the double mash method.
Grain Bill:    22 lbs Thomas Fawcett Maris Otter (floor malted) or other high quality Pale Malt.
                     2 lbs Roasted Barley
                     1/2 lb Chocolate Malt
                     1/2 lb Black Patent
                     1/4 lb rice hulls for second mash
Hops:          80 IBU's worth of a hop of the brewer's choice for bittering
                     1/2oz pelletized hops (brewer's choice) first runnings boil
                     2oz pelletized hops (brewer's choics) 10 minutes left in boil (flavor)
                     2 oz pelletized hops (brewer's choice) @ Flame Off (aroma)

White Labs English Ale Yeast or other Favorite UK strain, and a starter culture, for initial fermentation. It may be advisable to pitch yeast off of an actual freshly fermented batch transfered to secondary just prior to pitching into the imperial Stout.
White Labs Super High Gravity Ale, with starter, pitched into secondary after primary fermentation complete.

Mash in 13 lbs of base malt at 120F and hold for 10-15 minutes (dough-in, use just enough water to wet the grains)
Raise temperature slowly up to 155 F using remaining water and hold until conversion is complete. I usually do this in steps, where there is a rest in between where I take a temperature measurement, and hold for 5-10 minutes before adding more water to get the temperature up to 155. Once at this temperature get the sparge water ready. Time the final temperature increase with the sparge water becoming ready, with mash out being around 170F. Sparge and collect around 1.5 gallons of first runnings in the brew kettle, the rest into a second pot. Place brew kettle on a burner, add 1/2 oz hops. and boil until second mash is complete.

When sparging of the first mash is complete, bring wort up to mash in temperature and mash 9 lbs of base malt and the specialty grains with the rice hulls as above. Keep in mind slightly less sparge water is required as there is already some volume in the pot. Collect about 6 gallons total of wort in the brew kettle.

Boil for 15 minutes, then add bittering hops. Boil for 80 minutes and add the cooling coil to the pot for sanitization, along with the flavor hops. When the boil is done (after 10 more minutes), turn off the flame and add aroma hops. Cool and transfer to carboy. Aerate (we use a stone). Pitch the starter.

Fermentation usually takes about a couple weeks. It is helpful to use a carboy for fermentation so as to be able to observe fermentation activity. After 2 weeks, even if there is still activity, transfer to secondary to get beer off of the dead yeast, and pitch the Super High Gravity yeast. I recommend a transfer every 2 weeks to another carboy, to get the beer off the dead yeast. Keep an eye on the activity and bottle when still. This can take a few weeks so be patient. Bottle when ready.

OG usually ends up in the 24-27 Plato range. I don't measure the final gravity, as I find it to be a waste of beer, but ABV will be in the 10% range.

Notes:
1) Feel free to max out the hops, but this is basically the recipe I like.
2) Another method to flavor and aroma hopping this beer would be to add all or the late edition hops to the mash, and eliminate the late hops altogether. Not sure yet about which mash to add the hops to, and it may take a couple of years to figure all this out. Springtime will bring about a fresh batch with which to experiment.
3) I am using water in the 70-100 ppm solids range.
4) Try the Thomas Fawcett. It is a great malt! 
5) I have found that this beer, when fermented in the 68-73 F range, will be excellent to drink as soon as it carbonates, and only needs to age if I want to see what it is like in a year or two.