Process all cookie base ingredients into a sticky fine-crumb consistency (note:if the mixture seems a bit too dry, add another tbsp water, if too wet, adjust by adding a few more tbsp oats). Transfer this mixture into a parchment lined 7" x 5" tupperware container (or any dish of a similar size). Press down into a thin flat crust along the bottom. Freeze while working on the next step.
Blend all filling ingredients into a smooth consistency. Pour over the crust. Freeze overnight or for at least 6 hours to allow the mixture to set.
When ready to eat, cut into slices and enjoy! Keep leftovers frozen (they melt quickly!).