Sachetorte is quite dense and rich, and not overly sweet, so ideally it should be served in small slices with a little unsweetened whipped cream on the side, accompanied by a cup of coffee or tea. The sachertorte will improve in flavor if you make it a day or so before you want to eat it.
5 oz. unsalted butter, softened
1/2 cup fine sugar
1/2 tsp. vanilla extract
5 oz. bittersweet chocolate, broken into pieces
5 large eggs, separated, with the whites put into a large bowl
2/3 cup ground almonds
1-1/3 cups all-purpose flour
For the topping:
4 Tbsp. apricot jam, melted
5 oz. bittersweet chocolate, melted in a double boiler and then mixed with 3-1/4 cups plus 2 Tbsp. double cream
1. Preheat the oven to 350 degrees F. Grease and line a round cake pan. Beat the butter in a large bowl or mixer until it is really soft. Meanwhile, melt the chocolate in a double boiler.
2. Add the sugar to the butter and beat until the mixture is really light and fluffy. Add the vanilla extract and mix well. In a separate bowl, whisk egg whites until stiff.
3. Add the melted chocolate to the mix, then the egg yolks, one at a time, and the ground almonds and flour. Add about one third of the egg whites and stir well.
4. Fold in the remaining egg whites, pour into the pan and bake for 35 minutes. Once the cake is cool, brush the jam thinly over the surface, spread the chocolate and cream mix on top, and chill.