I came across the idea for this recipe quite by accident on David Lebovitz’s website. I am always a sucker for a flourless chocolate cake and, being intrigued by the notion of a reduced amount of processed sugar in exchange for the natural sugar of the prunes, I decided to give it a try. I used the chocolate that I had in the house, some “dark” chocolate from Callebaut (about 7 ounces) and some bittersweet chocolate from Scharffen Berger for the balance.
Although the original recipe called for the prunes to be chopped finely before being plumped in the rum, I chose to cook the prunes whole in the rum and then purée the cooked prunes and remaining rum juice with an immersion blender. In large measure this was because my household includes a rather fussy eight year old that doesn’t like finding chunks of anything but chocolate in his chocolate cake but I also had a sense that I would prefer the prunes to be more subtle ingredient in the cake.
By accident, I only put in half the butter (6 tablespoons as opposed to 12) called for in the original recipe but fortunately it still produced an acceptable result. My changes resulted in an almost mousse-like texture that I really enjoyed.
The cake is very moist, which makes for a challenge when trying to obtain clean cut slices. By dipping the knife in very hot water and then wiping it between each cut, you can get very good looking slices. I served the cake with unsweetened whipped cream. If I had it on hand, I would love it with creme fraiche.
For the prunes:
6 ounces (170g) pitted prunes
1/3 cup ( 80 ml) rum, or another liquor that appeals to you
1 tablespoon sugar
For the cake:
12 ounces (340g) bittersweet or semisweet chocolate coarsely chopped
6 tablespoons (3 ounces, 170g) unsalted butter, cubed
6 large eggs separated
large pinch of salt
3 tablespoons sugar
Additional soft butter and flour, or cocoa powder, for preparing the pan
Preheat the oven to 325ºF (165ºC).
Simmer the prunes with the rum and 1 tablespoon of sugar in a small saucepan for a few minutes, until most of the liquid is absorbed. Remove from heat, cover, and let stand until cool.
Butter a 9-inch (23cm) springform pan. Dust the inside with flour or cocoa powder, and tap out any excess. I prefer to use cocoa for this.
In a large bowl set over a pan of simmering water, melt the chocolate and butter, stirring until smooth. Remove from heat and stir in the puréed prunes.
Gently beat the egg yolks and stir into the chocolate mixture.
In a separate bowl, or using a stand mixer, whip the egg whites with the salt until they begin to hold soft peaks. Continue whipping, adding the 3 tablespoons of sugar, one tablespoon at a time, until the whites hold their shape when you lift the whip.
Fold one-third of the beaten egg whites into the chocolate mixture thoroughly, then gently fold in the remainder a third at a time just until no streaks of whites are visible. Don’t overfold.
Bake the cake for up to 40 to 45 minutes, or until the cake feels set close to the edges of the pan but the center is still rather soft to the touch and moist-looking. Mine took only half an hour to reach this stage, so keep a close eye on it!
Allow to cool. Run a thin knife around the cake to loosen it from the pan and remove the ring of the springform. The cake will keep for a couple of days, or if carefully wrapped it is suggested that it can be kept for up to 2 months in the freezer. (I can’t imagine getting it off the springform base intact to wrap it.)