Heat oven to 350 (180C) and line a cookie tray with parchment paper.
Using an electric hand mixer (or some serious elbow grease) cream the butter, brown sugar and Nutella until pale.
Mix in the egg then sift in the dry ingredients and mix well. Stir through the white chocolate.
Roll heaped teaspoons of the mixture into little balls (mine were a little under an inch in diameter) and place on the tray allowing room for spreading. Press down on each cookie gently with a fork.
Bake for about 12 minutes, turning the tray half way if your oven is not fan-forced. Allow to cool on the tray for a few minutes before turning out onto a wire rack.