Take a knife and shave a few pieces of chocolate then chop the rest.
Pour the water in a pan and bring to a simmer. Take off the heat, add the chocolate, stir until melted.
Pour into a bowl placed on top of another bowl filled with ice. Whisk until it starts to thicken.
Spoon into cappuccino cups, top with a teaspoon of yoghurt, then the hazelnuts and finish with chocolate shavings.