Cream the Stork and sugar together, gradually beat in the egg and vanilla essence.
Sift flour and stir into the creamed mixture with the oats, hazelnuts and chocolate, mix well.
Shape into a 2in/5cm diameter, 7in/18cm long sausage, wrap in cling film and chill for 30 minutes.
Preheat oven to Mark 5/190C/375F. Cut dough into 18, approximately 1/3in/1cm thick slices, place onto a Pyrex oven tray, leaving space between each.
Bake for 8 minutes or until firm around the edges and soft in the middle. Leave to cool on the baking sheets. Lift off using a palate knife and store in an airtight jar or tin. Cookies are best, eaten the same day.