1. In a small saucepan, cook chicken breast half in enough boiling water to cover for 15 minutes or until chicken is no longer pink (internal temperature should be 170 degrees F). Remove from saucepan; cool.
2. In a medium saucepan, cook the sweet potato, covered, in a small amount of boiling water for 20 to 25 minutes or until very tender. Drain sweet potatoes, reserving cooking liquid. Use a fork or potato masher to thoroughly mash potatoes.
3. Grind chicken in a food mill or mini food processor. Mix ground chicken and sweet potatoes together. Add 1/2 cup of the reserved cooking liquid or more for the consistency your child likes. Use within 1 day, or freeze up to 1 month.To Freeze:
4. Spoon finished food into ice cube trays. Cover with waxed paper and freeze until firm. When ice cubes are frozen, remove cubes from tray and store in a resealable plastic freezer bag or freezer container. Label package with contents and date. Use within 1 month. Before serving, let thaw in the refrigerator overnight.To Serve:
5. Heat thawed mixture to lukewarm in a small dish set in a pan of hot water. Stir before serving. Always sample a small bite to make sure the food is not too hot.