Milk Street: We were smitten with Claire Ptak’s chocolate, prune and whiskey cake, but when we got the recipe back to Milk Street we knew we needed to make adjustments. Most home bakers aren’t as skilled as Ptak, and we wanted a cake people would fall in love with on the first try – as we did when we tasted her version. Her cake is deliciously gooey at the center, and we wanted to keep that. A ratio of 3:1 chocolate to butter – as well as 8 ounces of chopped pitted prunes – got us the results we wanted. We tried a variety of chocolates and preferred bar chocolates with 60 to 70 percent cacao (especially the Ghirardelli and Guittard brands). Chocolate chips contain stabilizers that can change the cake’s texture; it’s best to avoid them. Ptak uses almond flour, not an uncommon ingredient in flourless chocolate cakes such as this, but certainly not a common ingredient in American homes. In an effort to streamline, we reworked the cake a bit to leave it out and found the results just as good. At first we questioned the need to whip the egg yolks and whites separately, but we discovered it made a big difference. Whipping the yolks helps maintain the emulsion of chocolate and butter; skipping that step produced an unpleasantly dense cake. And of course by now we understood the value of under-whipping the egg whites and just barely mixing them into the batter. Ptak originally made this cake with Armagnac, but later switched to whiskey. We couldn’t easily find the former, and the latter – while delicious once the cake was cooled – tasted harsh when the cake was warm (and this cake begs to be eaten warm). We found dark rum tasted delicious warm or cooled and better complemented the molasses.

1. 9 tablespoons salted butter (1 tablespoon softened)
2. 8 ounces pitted prunes (about 1 1/2 cups), finely chopped
3. 1/3 cup dark rum
4. 1 tablespoon molasses
5. 12 ounces bittersweet chocolate, finely chopped
6. 6 large eggs, separated
7. 1/3 cup plus 1/4 cup white sugar
8. 1/2 teaspoon kosher salt

1. Heat the oven to 325°F with a rack in the middle position. Coat the bottom and sides of a 9-inch springform pan evenly with the tablespoon of softened butter. In a 2-cup liquid measuring cup, combine the prunes, rum and molasses. Microwave until the rum is bubbling, 45 to 60 seconds. Let sit for 15 minutes, stirring occasionally.
2. In a medium saucepan over medium heat, melt the remaining 8 tablespoons of butter. Remove from the heat and immediately add the chocolate, then whisk until melted and completely smooth. In a large bowl, whisk together the egg yolks and ⅓ cup of sugar until pale and glossy, about 30 seconds. Slowly add the melted chocolate mixture and continue whisking until smooth. Stir in the prune mixture.
3. Using a stand mixer with a whisk attachment, whip the egg whites and salt on medium-high speed until light and foamy, about 1 minute. With the mixer running, slowly sprinkle in the remaining 1/4 cup of sugar and continue to whip until the whites are thick and glossy and hold soft peaks, about 1 minute.
4. Whisk 1/3 of the whipped egg whites into the chocolate mixture to lighten it. Gently fold in the remaining whites with a rubber spatula until the batter is marbled but not fully blended.
5. Pour the batter into the prepared pan. If needed, smooth the top with a spatula. Bake until the edges of the cake are firm and cracked, 35 to 40 minutes. The center will be just set, yet soft to the touch.
6. Cool the cake in the pan on a wire rack for at least 1 hour before serving (the cake will settle and sink as it cools).

• Don’t over-bake this cake. Don’t be alarmed if the center still jiggles a bit and yields to gentle pressure; the cake will continue to set after it comes out of the oven.