Blend all ingredients for the base in a food processor very well.
Spoon into a 9x9" square pan lined with parchment paper and spread into corners. Press down with your hands (or some other flat-based pan) to ensure the base holds together. Put in refrigerator while making the topping.
Blend all ingredients for the topping in the same food processor very well. Add sufficient milk to form a paste, but not too runny.
Press the topping down on the base until smooth.
Return to either the fridge or freezer until ready to eat. Cut into 12 bars with a sharp knife and store in either the fridge or freezer.