This is the fucking bomb. Like seriously, one of the best. If my memory serves me right, when we were kids- Rachel- the entrepreneur- would sell these for Passover. So when Jess P. said this was her favorite cake– even though I haven’t had Rachel’s in over a decade probably- I knew just who to ask for the recipe. The lovely Dolores lent me her springform pan for this- but it was so good- that after this, I went out and bought by own– so I can make this again and again.
1/2 lb. [2 sticks] unsalted butter, cut into small pieces, at room temperature
8 oz unsweetened chocolate
4 oz semisweet chocolate
1/2 cup water
1-1/3 cup sugar
5 extra large eggs at room temperature
Preheat oven to 350 degrees
1. Grease 9″ cakepan or springform pan [springform works best], and place a circle of parchment or waxed paper on the bottom that has been cut to fit. If waxed paper is used, grease that too- parchment paper doesn’t need greasing.
2. Chop both chocolates and set aside.
3. Combine the water w. one cup of the sugar in a heavy 2-quart saucepan. Bring to a boil over high heat, and cook about 4 minutes, or to a temperature of 220 degrees.
4. Remove the saucepan from the heat, and immediately add the chocolate pieces, stirring until they are melted and smooth. The mixture may “seize,” but that is all right. It will blend once the butter is added. Immediately start adding the butter, stirring gently until it is all melted in
5. Place the eggs and the remaining sugar in the bowl of an electric mixer. Start beating on high speed and continue until they are quite thick and pale yellow, and tripled in volume. This takes about 15 minutes [watched some madmen to occupy myself through this]
6. Start mixing egg and sugar mixture at slow speed. Add the chocolate mixture, stirring only until fully incorporated.
8. Pour the mixture into the prepared cake pan. Set the pan inside a slightly larger pan, and pour boiling water around it. Do not let the sides of the pans touch.
9. Place in the oven and bake 25 minutes. Insert a cake tester or point of a knife into the center of the cake. If it comes out clean, the cake is done. If not, continue cooking for up to 10 minutes longer. Do not cook longer than a total of 35 minutes.
10. Let cool in the pan for 10 minutes. Run a sharp knife around the edge of the cake and unmold onto a cookie sheet. Invert a serving plate over the cake, and turn it right side up.
Dust w. confectioner sugar.
Note: This cake may be eaten warm or cold, w. whipped cream and fresh fruit, or w. creme anglaise.
The texture of the cake will change if left overnight. It is still good- but firmer.
Snacko Backo 
Thanks Rachel – This cake was seriously amazing…so dense and creamy! Perfect really. Now I suppose I’ll have to get a springform pan now too…Wait. Does that say 2 STICKS of butter.
Yeah, I’m gonna need that springform pan back ASAP. After tasting this, I think I found a use for it.
Ok – so I’ve made this cake twice now (both times in an 8″ spring form). I would like to mention that in my most recent experiment I baked the cake for about 30 minutes, the cake tester came out clean, and cooled it for an hour. When I attempted to remove the spring form, the cake started to turn to liquid. Well after consulting Tessa I decided to try baking it again – which I did for about 25 more minutes. The cake turned out exactly as it should have originally much to my surprise. I just wanted to add this in case someone else runs into the same problem!
Also add- that you stored it in the fridge overnight- it’s the cold, i think- that helped keep it together. And I think that having the smaller pan- is effects the baking time/its ability to whole together.