Chop the chocolate as finely as you can

Put the sugar, water, coffee & vanilla extract into a small, heavy based saucepan and heat gently until the sugar and coffee granules have dissolved. Bring to the boil, then remove from the heat and let the syrup stand for 1 minute

Tip the chocolate into the syrup and use a stick blender to pulse the melting chocolate into the syrup. If you don't have a stick blender, then stir vigorously with a wooden spoon for 2-3 minutes until the chocolate has completely melted

Stir in the milk and add the hazelnuts (if using)

Decant into a jar and allow to set for around 4 hours

Store in the fridge for up to 2 week and bring to room temperature before serving