Preheat the oven to 350°F (175°C). Grease a 9-inch round cake pan and line the bottom with parchment paper.

1. Melt the dark chocolate in a heatproof bowl over a double boiler or in the microwave. Set aside to cool slightly.
2. Cream together softened butter and sugar in a large bowl until light and fluffy. Beat in the egg yolks, one at a time, followed by vanilla extract. Stir in the melted chocolate.
3. In a small bowl, whisk together the flour, cocoa powder, and salt. Gradually fold the dry ingredients into the chocolate mixture.
4. Beat the egg whites in a separate bowl until stiff peaks form. Gently fold the egg whites into the batter in three additions.
5. Pour the batter into the prepared pan and smooth the top. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean. Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
6. Once the cake is cool, slice it in half horizontally and spread apricot jam on the bottom layer. Place the top layer back on top and brush it with a thin layer of remaining apricot jam.
7. For the glaze, melt dark chocolate, heavy cream, and butter together until smooth and glossy. Pour the glaze over the cake, allowing it to drip down the sides. Let it set for 30-60 minutes at room temperature.
8. Slice and serve the Sacher Torte. It’s best enjoyed with a dollop of whipped cream or a scoop of vanilla ice cream.