Stir together all the cookie dough ingredients, then divide in half. Press one half into a lined baking dish (ours is 20x25cm) until a firm even layer is formed. Cover & store the other half of the cookie dough in the fridge to use later.
Add all of the icecream ingredients to a blender & blend until fully smooth (~2 mins).
Pour the icecream mix over the cookie base, cover & freeze until set (4 hours or overnight).
Once solid add the remaining cookie dough & press to form a top layer. Place back in the freezer for ~ 30 minutes, then remove & slice. Allow to soften for ~10 mins before slicing into ~16 pieces and serving (cut in half further for younger kids).
