Chocolate Prune Cake

Name: Chocolate-Prune Cake
Ingredients: 6 ounces (170g) pitted prunes (diced in small pieces); 1/3 cup ( 80 ml) rum (or another liquor (see headnote)); 1 tablespoon sugar; 12 ounces (340g) bittersweet or semisweet chocolate (coarsely chopped); 12 tablespoons (6 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)