Beat together the butter, sugars, egg and vanilla essence in a large bowl until smooth.
Stir in the flour and oats, then the dried cranberries and chopped hazelnuts.
Place teaspoonfuls of the mixture on to baking sheets lined with greaseproof paper or nonstick baking paper and flatten them slightly with the back of a fork.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for about 5–6 minutes until browned. Transfer to a wire rack to cool.