Preheat oven to 180°C or 160°C fan. Grease and line base of a 20cm springform pan.
Place chocolate, butter, sugar, whisky and coffee in a heatproof bowl. Place bowl over a saucepan of simmering water on low heat. Stir for 4-5 minutes, until chocolate melts and mixture is smooth. Remove from heat.
Whisk in egg yolks, one at a time, until smooth. Fold through ground hazelnuts. Using an electric beater or whisk, beat eggwhites until firm peaks form. Stir 2 tablespoons eggwhite into chocolate mixture. Gently fold in remaining eggwhite.
Spoon mixture into prepared pan. Bake for 50 minutes, until firm. Cool in pan for 5 minutes, then transfer to a wire rack to cool completely. Dust with cocoa and serve with thick cream.