Lightly oil a 13"x9" pan with a drop of coconut oil. Set aside.
Add cereal to a bowl and crush with hands until broken down. You can also use a potato masher.
Add crushed macadamia nuts (if using) and melted chocolate. Stir until everything is coated.
Press mixture into prepared pan and set in the fridge for 10 minutes to allow the chocolate to set. Remove from fridge and set aside on the counter.
Meanwhile, place frozen bananas in the bowl of your food processor. Pulse, on high, until broken down and creamy, but still frozen. If your food processor is having a hard time with this, add a splash or two of non-dairy milk. Any kind will do the trick.
Transfer banana soft serve to a tupperware container and store in the freezer while you cut the chocolate into twelve, 3"x3" squares.
Take two squares and spread the banana soft serve between the two to make sandwiches. Place on a parchment paper lined plate or, if you're planning to keep them in the freezer for awhile until serving, wrap each individually in foil, parchment paper or freezer wrap. Freeze until about firm, about 30 minutes.
Recipe by Healthful Pursuit at https://www.healthfulpursuit.com/2013/08/4-ingredient-vegan-ice-cream-sandwiches/