Mix the melted butter in a small bowl with the Nutella until smooth. Set aside.
Chop the chocolate with a good knife into small pieces.
In a saucepan combine the cream and vanilla sugar. Heat slowly to a boil. Pour hot cream over the chocolate and mix until all the chocolate has melted. Add the butter Nutella mixture and mix well.
Pour the ganache into a baking dish and refrigerate for 30 minutes or until cooled. Take out of the refrigerator and leave to rest for 15 minutes at room temperature. Transfer the ganache to the piping bag fitted with a plain 1/2-inch tip.
Holding the piping bag vertically, pipe using a squeeze and release motion in order to create a kiss.
Sprinkle the truffles nuts. Refrigerator until the truffles become firm.