Preheat oven to 170°C. Cream the butter and sugars for at least 5 minutes until the mixture becomes light and fluffy.
Add the egg and vanilla extract and beat well.
Add the white chocolate, cranberries, flour, baking soda and baking powder. Beat on low speed until just combined (don't overwork the mixture or it can become tough).
Dollop tablespoon sized balls of cookie dough onto lined baking trays.
Bake until cookies are golden around the edges, around 12-14 minutes.
Allow cookies to cool completely on a baking rack.