Place potatoes in a large saucepan and cover with water. Bring to a boil. Reduce heat; cover and simmer for 15-20 minutes or until tender. Drain and transfer to a small bowl.
Place the cilantro, garlic and salt in a small food processor; cover and pulse until chopped. Add water and vinegar; cover and process until blended. While processing, gradually add oil in a steady stream.
Using a fork, flatten potatoes slightly; pour sauce over top.