Flourless Chocolate Cake - Step-by-Step (with photos) (dial-up warning)
The following recipe is best attempted by those that are not only intimately familiar with the baking of cakes in general, but also love to bake. Otherwise, it might be too involved and advanced for the casual baker/cook. Just fair warning in case anyone makes it and ruins it on their first try 
It's not that bad (or hard) but I had also had years of experience at baking before I tried this one.
Flourless Chocolate Cake
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Pre-heat oven to 350 F (175 C)
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Standard measurements + (Metric measurements:)
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20 oz. (570 g) bittersweet chocolate
1.75 C (420 ml / 350 g) superfine sugar
((Superfine can be made by putting regular sugar in a food processor with a metal blade and pulsing for a couple of minutes until the sugar is of a finer grain than previously))
15 oz. (430 g) butter (unsalted)
15 eggs, whole - separated
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Equipment and pan(s):
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Large mixer with whip and paddle attachments, plus a bowl of 5 qt. (4.5 lt) capacity
Mixing bowl of at least 6 qt (5.5 lt) capacity for final mixing
Double boiler - can also use a large stainless bowl sitting over (not in) boiling water
10"x3" (25cm x 7.5cm) springform pan, buttered
(With buttered parchment paper fitted for bottom of pan)
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Directions:
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Melt chocolate in double boiler.
Whip butter and sugar, scraping sides as needed.
Remove whip attachment; use paddle.
Add chocolate to butter/sugar mixture.
Beat together, scraping sides as needed.
Add egg yolks one at a time, beating 20-30 seconds after each addition.
Transfer to separate bowl.
Clean machine bowl (or use second bowl if you have more than one.)
Whip egg whites.
Fold whites into chocolate mixture.
Pour cake mixture into pan, reserving one quarter of batch.
Bake cake at 350 F (175 C) for one hour.
Chill reserved batter.
Cool cake on rack. Cake will fall in middle. This is normal.
Chill cake in pan overnight (12 hours).
Level cake with top of pan; fill with chilled batter/frosting.
Unmold and serve.
NOTE: On these last two steps, I often unmold the cake first, then level the cake so that the leftover pieces can be fitted into the fallen portion in the middle, thus leveling it better. I then use a large flat frosting spatula I keep resting in hot water as I frost the cake with the remaining chilled batter. It also helps to leave the batter out for a few minutes, to help it soften up to a spreading consistency. Final decorations can be made with chocolate shavings pressed into the side of the cake. Pipe some ganache swirls evenly around the perimeter of the cake and you're done!
And now the photo-steps:
Prepping the chocolate for melting in my Cuisinart (fitted with the metal blade):
Some of the equipment and ingredients:
Separating the eggs:
Prepping the springform pan:
(I forgot to photo the pan buttered, but you can see a little of that after the batter goes in.)
Whipping the butter:
Melting the chocolate:
Whipping butter and sugar:
Melted chocolate:
Incorporating the chocolate into the butter and sugar:
Incorporating the egg yolks:
Batter ready for the egg whites:
Whipping the egg whites:
Egg whites finished to stiff peaks:
Folding egg whites into batter:
Weighing batter for later frosting:
Batter in the pan!
Freshly baked:
Cooling and falling:
Chilled cake:
De-panned:
Leveled with trimmed pieces fitted into the well:
Flipped over to reduce the problem with crumbs getting into the frosting:
This is my frosting spatula in boiling hot water and an insulated sleeve around the canteen:
The frosting:
Fully frosted:
Decorating prep (the ice pack is to chill my hand just before I press the white-chocolate shavings into the frosting):
Decorating, with a parchment-lined sheet pan below to catch the dropped shavings:
The finished cake!
The only real difficulty left is to get it to the cafe of some friends without me taking corners like I normally do! 
= new reply since forum marked as read
Good JOB 
Great pictorial as well.
As much as I like to bake this seems time consuming.
I really need to get that shredder. I wonder if I could borrow one from the Republicans. I need an industrial-sized shredder 
Thanks, too 
Time-wise, other than the 12-hour chillin' time, it's about 3-4 hours: two hours to make and two hours for frosting/decorating. I'm including the time spent shaving chocolate as well as making other decorations, like curls and sheets for cutouts 
they'd likely agree with you! 
If I had a video camera (and someone to hold it) I'd have done the demonstration that way. I think that would help the most, especially for those that might not be tempted to try it even with a good baking background. All I was ever given was the recipe, so I had to teach myself. However, as I recall, I know I read the recipe many times and then made sure I had everything ready and together before I started. That way, mistakes were at a minimum. Mise en place
I'm surprised no one caught my little 3 Stooges nod with the "separating the eggs" images
the difference with the actual soufflé version is that they want the egg white mixture to keep its structure after cooking. The sugar is the key to that (the lemon juice is more to help the whites froth up, kind of like how a copper bowl makes better meringue than any other kind.) The protein in the whites combine with the sugar during cooking and "fix" the structure in place. It's delicate, but with care will hold its shape until eaten.
Whereas the whites in my recipe add structure mainly to the batter as a kind of buttercream frosting, and only rise in the baking while falling at the end. Soufflés aren't meant to fall
The resulting texture of the cake is kind of like a drier brownie. However, due to all the butter and yolks, it tends to kind of melt in your mouth. It may fool someone with celiac disease, as the texture is certainly "cakey" at first. If any of y'all make this, you might need to have a copy of the recipe handy to convince someone with a wheat sensitivity
I've never made any kind of soufflé, but I do have eggs leftover (I don't really eat them anymore, except within something baked.) Maybe that can be my next project
I'm sure you'll love it
And I've recently started using a term for cakes like this in order to describe their sweetness factor and flavoring: they're "European sweet" not "American sweet".
While I know many of us probably hate cakes and other sweets that are overdone in the sugar department, that fact doesn't seem to have hindered your average chain restaurant or supermarket-bakery from dumping twice as much sugar as is needed into their products.
I don't know who started that or why, but it's in the opposite direction from everything I've ever known about European cakes, like a genoise layer cake with buttercream frosting. The sugar is subdued in order to allow the flavors to come out. The added fats enable that, and such is the case with this cake. Lots of fat, less sugar, and lots of flavor!
I may have to experiment with this and see if there's a way to make it like a brownie...
now I think I understand--finding really good instructions and following them exactly is key to greatness in the kitchen, right? This sounds delectable, BTW
in how to make this. Not because I wouldn't be available if any of y'all have questions (I am here on DU most of the time), but it's always so satisfying to do it on your own then you have good instructions
When my friends opened the cake box, they asked me where I bought it! 
If you do make it, have fun, put on some good music (when you can hear it over the machines!) and make a cake you may never forget
