Add the double cream and half of the condensed milk to a large bowl, and whisk for several minutes until thick and frothy - you should be able to write your name with the mixture that drips from the whisk before it sinks in.

Add the rest of the condensed milk and all of the avocado flesh to a blender, and blitz thoroughly until smooth.

Add the blended avocado and vanilla extract to the whipped cream, and fold together gently until completely combined. Transfer the mixture to a loaf tin or other suitably sized container, and add a lid or cover tightly with foil.

Place in the freezer overnight, or until completely frozen.