Preheat the oven to 190°C and line a 23cm cake tin with parchment.
Melt the chopped chocolate in a bowl over a pan of simmering water.
Separate the egg whites and yolks into two different bowls.
Remove chocolate from heat and beat in the butter until incorporated.
Whisk the sugar and egg yolks together until pale and thick.
Fold the chocolate, hazelnuts, flour, and orange liqueur into the yolk mixture.
Whisk egg whites with salt until stiff peaks form.
Gently fold the egg whites into the chocolate batter.
Pour the batter into the tin and bake for 40 to 50 minutes.
Cool the cake for 10 minutes before transferring to a wire rack.
Melt the glaze chocolate over simmering water.
Beat the butter and liqueur into the melted glaze chocolate.
Spread the thickened glaze over the cake and decorate with whole hazelnuts.
Serve the torte with freshly whipped cream.