SacherTorte (chocolate cake) was invented in 1832 by Austrian Franz Sacher. It is one of Vienna’s most famous culinary specialties and even in the United States, Sachertorte day is celebrated in December 5th. Although many interpretations of this cake exist, the original recipe is a secret protected today and served exclusively by the Sacher Hotels in Vienna and Salzburg. Though, Lenôtre, Pierre Hermé and Alain Ducasse have made their reputations in this matter. They all share the same recipe protocol based on a high quality almond paste and egg mixture emulsion and meringue which give the sponge its incredible texture and flavor. The Sachertorte is originally layered with apricot jam. Chocolate ganache or mousse are a great addition to balance out flavors and textures. Some recipes can be found with passion fruit mousse, or cherry amaretto, or raspberry. Its intense almond-chocolate flavor allows many possible combinations. In France, Sacher biscuit is widely used as a base for many entremet and petits gâteaux.
Use high quality almond paste (50%/70%) such as Lubeca cut into cubes. Sift flour with cocoa powder; set aside. In a separate pastry bowl, mix eggs and yolks; set aside. In the stand mixer fitted with the paddle attachment, mix cubed almond paste with powdered sugar. Add egg-yolk mixture very slowly at the beginning making sure it turns smooth before adding more. Once the egg-yolk mixture is fully absorbed, turn off the mixer, scrape down the sides of the bowl and switch with the whisk attachment – beat on high for about 10 minutes. Transfer almond mixture in a large bowl and clean the mixing bowl. Turn oven on to 380ºF/190ºC. Make a meringue with the egg whites and sugar. Fold one-third of the meringue into the almond mixture, and add the sifted flour-cocoa powder and fold in remaining meringue – add melted butter. Spread Sacher biscuit evenly onto the tray ending up with a ≈(1/2''/1.25cm thick sheet.
Bake for 10/12 minutes. Cool to room temperature and chill. Sacher biscuit can be made days ahead and kept refrigerated or frozen. Top biscuit with a parchment paper and flip; remove silicone mat. Divide biscuit into 3 equal portions. Spread apricot jam generously and chill or freeze for 30 min before montage.
Soak gelatin in cold water to soften, and drain. Melt chocolate and keep warm at ≈113ºF/45ºC. In a stand mixer fitted with the whisk attachment, whip heavy cream to soft peaks; transfer in bowl. Clean up the mixing bowl and thrown in eggs and yolks, and beat on medium speed. Meanwhile, in a small saucepan, cook sugar and water to 262ºF/128ºC. Set speed on high and pour cooked syrup in thin stream – add the softened gelatin (liquify soften gelatin in a microwave for ≈2 sec) and beat until it cools; for about 10 minutes. Transfer egg mixture (pate a bombe/sabayon) in a large bowl and set aside. In the melted chocolate, whisk in a couple of tablespoons whipped cream – fold in sabayon and add the remaining whipped cream; chill the mousse to harden prior using.
Make a ganache: melt chocolate over water-bath. Mix in hot heavy cream; set aside. Meanwhile, cook sugar and water in large saucepan – let boil for a minute and stir in cocoa powder (do not incorporate too much air bubbles while stirring up). Give a boil and remove from the stove. Add creme fraiche and ganache. Smooth out with an immersion blender keeping the nose down, sieve and cool. Use at 113ºF/45ºC.
Place the first Sacher biscuit on a platter with the apricot jam already on. Pipe out the first layer of chocolate mousse. Repeat until done and freeze for 30 min. Top cake with a thinner layer of chocolate mousse and coat the edges as well; square it and freeze for at least 6 hours before glazing. Any cake should be hard frozen before being glazed. Trim off cake edges and glaze. Use chocolate glaze at 113ºF/45ºC. Finished Sachertorte can be kept refrigerated for up to 3 days or frozen for weeks. Thaw cake before cutting. Enjoy!