In the past few years, bakers have been upping the ante with chocolate desserts (think of your local American bistro’s “warm chocolate cakes with gooey chocolate centers”). The Sachertorte is a refined, elegant combination of chocolate flavors, complemented by a compulsory mound of Schlag. The whipped cream is an important part of the picture, as it moistens the frankly firm cake layers. Every bite of Sachertorte is supposed to be dipped in the whipped cream. This version is based on the recipe in Das Große Sacher Backbuch (“The Big Sacher Baking Book”), which should be a reliable source.
Don’t expect the cake layer to look perfect; sometimes the air bubbles are large and make holes in the top of the cake. If that happens, take some cake trimmings and mash them with a little of the apricot glaze to make a paste, and use a metal icing spatula to “spackle” the holes with the mixture.
To make the torte: Position a rack in the center of the oven and heat to 350°F. Lightly butter a 9-inch springform pan and line the bottom with a round of parchment or wax paper. Dust the sides of the pan with flour and tap out the excess.
In the top part of a double boiler over very hot, but not simmering, water, or in a microwave at medium power, melt the chocolate. Remove from the heat or the oven, and let stand, stirring often, until cool.
Beat the butter in the bowl of a heavy-duty standing mixer fitted with the paddle blade on medium-high speed until smooth, about 1 minute. On low speed, beat in the confectioners’ sugar. Return the speed to medium-high and beat until light in color and texture, about 2 minutes. Beat in the egg yolks, one at a time, scraping down the sides of the bowl. Beat in the chocolate and vanilla.
Beat the egg whites and granulated sugar in a large bowl with a handheld electric mixer on high speed just until they form soft, shiny peaks. Do not overbeat. Stir about one fourth of the beaten whites into the chocolate mixture to lighten it, then fold in the remaining whites, leaving a few visible wisps of whites. Sift half of the flour over the chocolate mixture, and fold in with a large balloon whisk or rubber spatula. Repeat with the remaining flour.
Spread evenly in the pan. Bake until a toothpick inserted in the center comes out clean, about 35 minutes. (The cake will crack on top.) Cool on a wire rack for 10 minutes. Remove the sides of the pan, and invert the cake onto the rack. Remove the paper and cool completely, leaving the cake upside down.
To assemble: Cut the cake horizontally into two equal layers. Place the bottom layer on an 8-inch cardboard round. Brush the top of the cake layer with the apricot glaze. Place the second layer on top, smoothes side up, and brush the top and sides with the remaining glaze. Transfer the cake to a wire rack placed over a baking sheet lined with wax paper. Let cool until the glaze is set.
Make the chocolate glaze (it must be freshly made and warm). Pour all of the warm chocolate glaze on top of the cake. Using a metal offset spatula, gently smooth the glaze over the cake, allowing it to run down the sides, being sure that the glaze completely coats the cake (patch any bare spots with the spatula and the icing that has dripped). Cool until the glaze is set, trimming off any drips of icing around the bottom. Transfer the cake to a serving plate.
To serve, slice with a sharp knife dipped into hot water. Serve with a large dollop of whipped cream on the side.