This is really easy and fabulous. This is an adaption of a recipe from Good Housekeeping that is in turn a tweaked version of a famous (or infamous) cake from the River Cafe in London. For some reason, the recipe is not posted on the magazine’s website, so you need to go to Frazzled Dad or Jewish Food List for this recipe.
I have made this many, many times and have worked out my own touches. First of all, I scale it down and bake in a 8″x3″ round pan. A springform pan will work, too, provided that you wrap the bottom with foil before baking it in the water bath. The batter will also just fit in a regular 8″ round pan.
Here is the ingredient list:
12 ounces bittersweet chocolate (I like 4 ounces 60/40 Callebaut and 8 ounces of 813 Callebaut), chopped (5 ounces Alprose 50% and 7 ounces 60% Passover chocolate works, too, as does a mix of Shmerling 72 % and 50% chocolate)
6 ounces margarine or butter
6 Tbl. water
3/4 cup sugar (divided: half is for the eggs and half is for the syrup)
5 eggs, room temperature
Here is what you do: boil the 6 Tbl. water with 6 Tbl. of the sugar. I let this boil for 5 minutes based on a tip I found somewhere regarding this cake. Remove from heat. Add the margarine (or butter) and chopped chocolate and stir to thoroughly melt everything into a smooth mixture. Let this melted chocolate mixture cool for about a half hour.
Meanwhile, beat the room temperature eggs with sugar until the mixture has dramatically increased in volume and lightened in color. It should be a very pale yellow and be very, very thick. This should take 5-10 minutes.
Now you need to fold the chocolate and eggs together. You can just dump the melted chocolate into the eggs and then use a whisk to lift up the chocolate from the bottom of the bowl (where it will immediately sink) and combine it with the eggs. I sometimes take some of the eggs and stir them into the chocolate to lighten the chocolate mixture before adding it to the eggs. I also whisk for just a short amount of time and then switch to a spatula to finish folding. Sometimes, I just use a spatula to fold everything together.
Try to be as gentle as possible to avoid losing too much volume.
Pour the mixture into a 8″ round pan lined with parchment (you can use a deep foil casserole pan as well as a regular cake pan). For easiest release, line the bottom with TWO parchment circles and line the sides with a double layer of parchment as well. Grease the pan before adding the parchment, and then spray the inside of the parchment lined pan before adding the batter.
Place the cake pan in a roasting pan filled with water. How much water? Enough so that when you put the cake pan in the roasting pan the water comes up about halfway the sides of the pan. You can add the cake pan to the roasting pan and then add the water, but be careful not to spill water on the cake.
Bake the cake at 325 degrees for 30 to 35 minutes. The top of the cake should be set (although I have taken it out when the very center of the top looked a bit wet and it was okay). It won’t look done. It will slosh a bit if you gently shake it. Let it cool and refrigerate overnight before attempting to unmold. I have been able to unmold this after a couple of hours in the fridge, but this is a slightly risky thing to try. The chocolate needs to set up in the fridge to facilitate easy unmolding.
Note: You can also bake this at a slightly higher temperature for slightly longer. Raising the temperature to 350 for the last ten minutes gives a firm crust.
Try to let the cake sit out at room temperature for about an hour before serving for optimal taste.
Note: I had a problem once with the chocolate breaking down when I was melting it. I added it to the sugar syrup before the margarine and I think the chocolate overheated. Generally, I add the margarine first and then the chocolate. Regardless, I had a mess on my hands–the chocolate had separated into solids and melted fat. I added a couple of Tbl. of boiling water and then took an immersion blender to the mixture. It became extremely smooth. Later, I found this post on Sweet Napa which confirmed that the immersion blender is a good way to go. This Sweet Napa post has very good tips for dealing with ganache.