Begin by melting the dark chocolate and butter together. You can do this by placing them in a bowl over a pot of simmering water. Stir occasionally until the mixture is smooth and well combined.

In another bowl, whisk together the sugar and eggs until the mixture turns pale and creamy.

Once the chocolate and butter have melted, slowly combine this mixture with the whisked eggs and sugar. Mix everything together until it is evenly blended.

Break the digestive biscuits into small pieces and fold them into the chocolate mixture. If you’re using nuts, chop them up and add them as well. Stir gently until the biscuits and nuts are mixed in thoroughly.

Take the mixture and shape it into a log. Wrap the log tightly in parchment paper.

Place the wrapped log in the refrigerator and let it chill for about 4 hours or until it is firm to the touch.

Once firm, remove the log from the fridge and unwrap it. Dust the outside with powdered sugar for a snowy finish before slicing it into thick rounds.