Moist Cake with Chocolate & Hazelnuts

Preheat the oven to 180°C (thermostat 6).
Melt chocolate with butter in a bathtub or microwave. Mix until the mixture is smooth.
Add the eggs one by one to the melted chocolate, whisk well between each addition.
Add sugar and mix until the mixture is homogeneous.
Add flour, yeast chemical and a pinch of salt. Stir gently to avoid lumps.
Add crushed hazelnuts and mix.