I like being fashionably late, so this is totally appropriate.
You should make this cake anyway, because it tastes like Katherine's brownies. Make it for your favorite gluten-free friend or family member, or make it for yourself and hoard the entire thing. Just make it, ok?
Flourless Chocolate Cake (from Williams-Sonoma)
Unsalted butter for greasing the pan
Preheat oven to 375*. Grease an 8-9" springform pan with a little butter. Fit a piece of parchment paper into the bottom, and set aside.
In a double boiler (or a pot with a few inches of water, with a heat-proof bowl on top), bring water to a simmer in the bottom pot. It's really important for the heat to be pretty low during this step, otherwise you'll kill the chocolate and have to start over again. Melt chocolate and butter together, whisking pretty consistently, until it's completely melted. Set aside to cool for at least 5 minutes.
While the chocolate is cooling, whisk cream of tartar/vinegar and egg whites with your mixer on medium-high for a minute, until frothy. Add half the sugar and whisk for 15 seconds, then add the rest of the sugar. Whisk for a few more minutes (mine took 2-3), until the egg whites are shiny and hold a stiff peak.
In a large measuring cup, lightly whisk together egg yolks, vanilla and coffee. Very slowly pour into the cooled chocolate mixture and whisk until no yellow streaks remain. If the chocolate is anything more than warm, pour a little into the egg mixture first and stir it in to bring the eggs up to temperature a bit (tempering). Then pour everything (still very slowly) into the chocolate.
Fold about 1/3 of the egg whites into the chocolate with a rubber spatula, until no white streaks remain. Fold the rest of the egg whites into the batter, until again no white streaks remain. Pour batter into the pan and distribute evenly. Bake 20-23 minutes, or until the cake is just slightly jiggly in the center (if it's completely set it'll be too overdone once cool). Move the pan gently side to side to check. Don't move it too hard though, or you'll shake the air right out. Once the cake is done, let it cool in the pan for about 30 minutes. It will sink a little (maybe 1/2"), that's normal. Carefully remove from the pan (this is where the parchment paper comes in handy) and let it cool the rest of the way on your serving dish. Enjoy with some fresh strawberries and/or whipped cream! I'd totally go with and over or.