This same method can be used to make a green pea puree for babies.
Arrange beans on a steamer rack in a large pan over 1 inch of water. Cover, and bring to a boil. Reduce heat. Steam until tender, about 8 minutes. Plunge beans into cold water to stop cooking. Pulse in a food processor, or pass through a food mill fitted with a medium disk. Add formula, breast milk, or boiled and cooled water as needed. Fill 1/4-cup plastic containers or ice-cube trays with puree.