Preheat your oven to 160℃/320℉ (or if you're using a fan/convection oven, set it to 140℃/290℉). Line an 8x8-inch tin with baking paper.
In a large bowl, mix together the melted butter, caster sugar and brown sugar. Then stir in the eggs and vanilla extract.
Add the flour, ginger, cinnamon and nutmeg and mix well to make a smooth blondie batter.
Crush up 1 pack of the Oreos and fold them into the batter along with the white chocolate chips.
Transfer to your lined tin and spread out evenly. Top with the other pack of Oreos, using as many as you like.
Bake for 35-40 minutes, until they're golden brown all over and pulling away from the tin slightly.
Leave the blondies in the tin to cool completely then put them in the fridge for 3-4 hours to set. This will make the gooey centre turn firm and fudgy.
Once set, cut into squares and enjoy!