Peel, de-seed, and dice a medium butternut squash. Place steam basket in a pot with water and steam cook squash for about 15 minutes, or until very tender. Transfer to a mixing bowl. (may also roast in the oven at 350 degrees for 1 hour)
Preheat oven to 325 degrees F and grease a glass 8 x 8 baking dish with coconut oil. Set aside.
Add the eggs, egg yolk, banana, and coconut oil to the mixing bowl with the squash. Blend with an immersion blender until very smooth. (May alternatively blend in a blender or food processor, or with hand mixer)
Pour batter into prepared dish and spread evenly.
Bake for 35 minutes until the egg is set and the batter is solid.
Allow to cool and cut into small squares.
Freeze individual squares in an airtight container; reheat to serve.