Preheat oven to 180°C/160°C fan-forced

Grease and line a 20cm square cake pan with baking paper

Place chocolate in a heatproof bowl over a saucepan of simmering water. Stir until smooth

Scoop avocado flesh into a large bowl and add lemon juice

Using a stick blender, blend avocado until smooth (it is important to not have any lumps)

Add sugar, eggs, cocoa, flour, baking powder and chocolate to avocados. Mix until well combined

Pour mixture into prepared pan. Bake for 25 minutes or until just set. Allow brownie to cool completely in pan

Place ice-cream into a bowl and stand at room temperature until just softened

Scoop avocado flesh into a bowl; add lemon juice and mash until almost smooth

Stir avocado through ice-cream until just combined

Scoop into an airtight container

Freeze for 3-4 hours or until ready to serve