I've heard you can water plants with potato water that came from boiling your potatoes. Are there any real benefits of this and how should I go about doing so?

Several gardening sources suggest that using water from boiling potatoes, for use in watering plants is beneficial. This makes sense, as potatoes are nutrient-rich with potassium, magnesium, phosphorus and a host of other vitamins and minerals. The only caveat I might suggest is to (obviously) let the water cool down first, and refrain from this application if the potato-water contains seasonings.