I don't know how many of these columns I've written by now, but I feel pretty confident that this will be the one I get the most "what kind of brain trauma has this idiot suffered that he thinks this is the best version?" e-mails about. Much like my disclaimer at the top of the American IPA piece, I'll preface this by saying that there are a lot of paths to the top of the mountain when it comes to Double IPA.
You may think I'm wrong here, and you may well be right, but I'll stand by this recipe as an as-good-as-any (and better than a lot) example. Double IPA is about more than just shoveling in hops. I don't actually think it's that controversial to state that I'm probably disappointed more often with commercial Double IPAs than any other style, especially when they're just a sweet, hot, bitter mess. I can't promise you you'll brew the next Pliny the Elder, but I can promise that this will get you close enough to your ideal Double IPA that you can adjust your recipe the rest of the way in.
The basic style parameters here are actually pretty simple: very high ("…to absurdly high") bitterness, intense hops aroma and flavor (usually American or Australian or New World hops), with just enough malt character to provide some background and/or contrast. What is usually overlooked, though, is that this is not an intensely alcoholic beer. Strong to very strong versions exist, but the guidelines place the ABV range for Double IPA at 7.5-10 percent.
That's stronger than most "common" ales, but it's not a mandate to load down your beer with warm, sweet ethanol, and doing so often leads to poor attenuation and harsh alcohols that take smooth but intense bitterness and translate it into sharp, peppery harshness. Without the benefit of (or desire for) a rich malt backbone, it can be very easy to go overboard on both alcohol and hopping in this style. Resist the urge. Aim low.
I like to keep this beer simple and clean in the grist: just some light toasted biscuit and grain flavors. Thirteen pounds (5.9 kilos) of Pilsner malt, then half a pound each (0.23kg) of Caramunich and British Crystal 45 get me to an OG, post-boil, of 1.076 and a potential ABV of about 7.9 percent. I know a lot of recipes call for simple sugar here, but I don't like it. If your fermentation gets away from you at all it's too easy to develop hot alcohols, and simple sugars increase the risk. You should be able to ferment this out nice and clean and dry, without the crutch.
Hopping is where this beer is made, though. Keep in mind that the flavors should be complex, not just prominent. We start with bittering, though: 40 IBUs from the highest-alpha hops you can get your hands on, to start, at 60 minutes. That will keep the amount of plant material down, and there's already going to be plenty, even if you stick with pellet hops. Then I add an ounce (28g) of Amarillo with 30 minutes to go, just for some fruity background flavors (and some more IBUs, about 28).
The rest of your hops should come at flame-out, and use more than one. My favorite combination is Citra, Motueka, and more Amarillo, in equal parts. I add three ounces (one ounce each) in the whirlpool, then dry-hop with one more ounce of each. The timing and order seem to matter here. I add the Amarillo at the end of fermentation, then the Citra five days after that, and the Motueka five days after that - and then hold for three days. The result is a bright, citrusy, lightly-floral hops aroma and flavor.
And ferment this out with the cleanest, best-performing yeast you have in your arsenal. I'll put in a pitch (pun intended) for Wyeast German Ale (1007), but the important thing is to choose the yeast that, in your system and process, gets you the best attenuation with the least impact on flavor. We want dry and clean.
All pellet hops here, to keep the amount of "plant" down (too much hops material can create cabbage-like flavors). If you don't ordinarily bag or spider or strain your hops, you may want to think about it just for this beer, since otherwise you might end up with trouble racking/siphoning/draining off after the boil.
Ferment cool but not cold here - we don't want to stall the yeast. I like starting at 62F (17C) and holding there for 48 hours, then ramping up by one degree per day for a week. That should encourage healthy attenuation and also limit off-flavors and/or their precursors. Don't rush it, either, even to preserve the hops flavor: a dirty Double IPA isn't good, no matter how fresh the hops seem. Let it ferment out fully, and trust your late dry hops to hold up.
Cold crash, then package and carbonate to 2.5 volumes of CO2. Don't worry too much about clearing it - some amount of turbidity is fine, and if you suck up some hops it won't hurt. I will, though, make a pitch for keg conditioning here. There's no question this style is best fresh, and while it will keep longer than you might think (especially at near-freezing temps) the quicker you start to drink it, the better it's likely to be.
Don't cave to peer pressure and treat this like an "Imperial" beer first and an IPA second. Make a great IPA first, and then warm it up. I think you'll be glad you did. Now let's get that hate mail feedback coming on in.