100²µ/3½´Ç³ú chocolate hazelnut spread (optional)
100²µ/3½´Ç³ú plain flour
¾ tsp baking powder
50²µ/1¾´Ç³ú cocoa powder
100²µ/3½´Ç³ú hazelnuts, roughly chopped
50ml/2fl oz hazelnut liqueur (optional)
pinch salt
250g/9oz granulated sugar
300²µ/10½´Ç³ú dark chocolate, at least 70% cocoa solids
250g/9oz butter
4 free-range eggs