Begin by melting the dark chocolate. Once melted, pour it into a cake tin, spreading it evenly. Place the tin in the refrigerator for 5 minutes to allow the chocolate to set slightly, then repeat this process once more.

In a separate bowl, melt the white chocolate. Mix the melted white chocolate with hazelnut cream and chopped hazelnuts until well combined.

Pour the white chocolate and hazelnut mixture over the chilled dark chocolate layer in the cake tin. Spread it evenly, then place the tin in the freezer for 5 minutes to allow the mixture to firm up.

Once the white chocolate layer has set, cover it with another layer of melted dark chocolate. Ensure the entire surface is covered evenly.

Refrigerate the cake for a few hours, or until the chocolate has completely set.

Once set, remove the cake from the tin, slice, and serve. Enjoy your delicious Chocolate Hazelnut Biscuit Cake!