Stir together all cookie dough ingredients, then divide in half. Press one half into a firm even layer in a lined baking dish ours is 20x25cm. Cover & store the other half in the fridge for later.
Add icecream ingredients to a blender & blend until fully smooth (~2 mins).
Pour the icecream over the cookie base, then blend the mango until smooth (we do this in a jar with a stick blender) and swirl through the icecream. Cover & freeze until set (4 hours or overnight).
Once solid add the remaining cookie dough to form a top layer. Place back in the freezer for ~30mins. Allow to soften at room temp for 15mins before slicing and enjoy!
Store leftovers in an airtight container in the freezer for up to 2 months.