Set the basket of a steamer over a pot of water and bring to a boil.
Rinse your green beans, then trim off the ends. Cut into halves or thirds, depending on how long they are.
When the water is boiling, add the green bean pieces to the steamer basket, and cook for 10-15 minutes, or until tender.
Reserve some of the cooking water and set aside, then drain the green beans.
Add the green beans to your blender or food processor and blend, adding water as needed to move things along.
Using a tablespoon, spoon the mixture into an ice cube tray. Smooth the top of each cube with a rubber spatula, then freeze.
Once fully frozen, remove green bean puree cubes from the ice cube tray and transfer to a storage bag, then return to the freezer. Use as needed.