One of the easiest flourless chocolate cake recipes you'll ever make, with a cracked top and soft, intense chocolate middle. Serve warm, with a scoop of ice cream or simply dusted with cocoa or powdered sugar.
Position rack in the lower third of the oven and preheat to 375 (190C) degrees.
Line the bottoms of 4 (4-inch) mini or 1 (8-inch) springform pans with a round of parchment paper. Brush softened butter all over the inside of the pan. Place the pan(s) on a baking sheet.
Combine the chopped chocolate, cocoa, 1 cup of the sugar and the salt in a large mixing bowl. Pour the boiling water over and whisk until mixture is smooth and the chocolate is completely melted. Whisk in the egg yolks, vanilla extract and almond flour. Set aside.
Beat egg whites in the bowl of an electric mixer fitted with the whisk attachment until soft peaks form. Gradually sprinkle in the remaining ¼ cup sugar and continue beating until stiff but glossy.
Fold about ¼ of the egg whites into the chocolate mixture to lighten it. Fold in remaining egg whites. Spoon the batter evenly into the pans.
Bake for 20-25 minutes for 4-inch cakes or 30-35 minutes for the 8-inch cake, or until a toothpick or wooden skewer inserted into the center comes out with moist crumbs clinging to it. Cool on a rack 5 minutes. Remove sides of pan.
Slide a small knife or spatula under the cakes to release them.
Serve warm or at room temperature, sprinkled with cocoa and/or powdered sugar, if you like.
Serving idea:Bake the cakes in 8-ounce ramekins (20-25 minutes) and serve warm right out of the dishes, with a scoop of ice cream.To make ahead:Fill the pans with the batter and refrigerate up to 4 hours in advance of baking.Adapted from a recipe by Alice Medrich.