For the mango filling:
In a high speed blender blend the fresh bananas until liquid. Add frozen mangos and blend until velvety smooth pausing to stir if necessary.
For the cookie base:
In a food processor combine oats, walnuts, flax and pitted dates. Blend on high until crumbly.
Press cookie crumble into parchment or silicone cupcake liners, pipe or spoon in mango filling and freeze one hour or until firm.