Cream together the butter and sugars in a medium sized mixing bowl. Mix in the egg and vanilla.Add the flour and baking soda to the bowl and fold together with a wooden spoon until the flour is almost incorporated.Add the white chocolate and cranberries and fold the cookies dough together until fully combined.Roll out 1 Tablespoon sized cookie dough balls on a baking sheet, leaving room for the cookies to spread, and bake in a 180C|350F oven for 8-9 minutes or until the edges start to brown.