Preheat the oven to 150 C. Line a 23cm x 28cm rectangular cake tin with baking parchment.
Combine the flour, and butter cubes in a food processor and pulse until the mixture resembles fine breadcrumbs.
Add in the caster sugar and pulse again until combined. Tip the mixture into the lined cake tin and spread it out evenly with the back of a spoon then add 50g of white chocolate chips to the top.
Then press the shortbread down firmly with your knuckles so that it is tightly packed in the tin.
Bake the shortbread for 30 minutes or until very light golden brown. Set aside to cool.