Preheat the oven to 190°C. Prep two baking trays with greaseproof paper and set aside.
In a bowl, cream together the butter and sugar until light and fluffy.
Next add the egg, vanilla extract and give it a good mixture until well combined.
Then add the flour, baking soda and salt and form a dough.
Finally mix in the chopped walnuts and sultanas.
Divide the dough into 20 balls and place on the baking tray leaving some space in between.
Flatten each one cookie dough ball and bake for about 12-15mins until the cookies are slightly golden brown.
Cool them on a baking tray and store them in an airtight container.