Boniatos are a variety of sweet potato (Ipomoea batatas) also known as batatas, tropical sweet potatoes, or Cuban sweet potatoes. The roots look very similar to sweet potatoes; they are about fist-sized in diameter and two fists long with an irregular, bumpy shape. However, boniatos have a bright red thin skin and white, creamy flesh while sweet potatoes have an orange-brown skin with yellow or orange flesh. The boniato plant is native to the tropical regions of Central America and has spread to the Caribbean, Mexico, and regions in the United States, especially in Southern Florida.
Boniatos are available year-round but because they can easily spoil they are rarely found outside their growing regions. If you are buying boniatos, look for ones that are firm and unblemished. You can store them in the fridge for a week or two, but sources indicate the best storage place is in a cool, dry pantry.
Boniatos can be used in any dish that calls for sweet potatoes. The roots have a similar overall flavor as sweet potatoes but they tend to be drier, less sweet, and have a fluffier texture. When you cut up a boniato, be sure to submerge the pieces in cold water to prevent the white flesh from turning blue or gray. You can mash them and serve them like mashed potatoes, bake or roast them in the oven, or cut them into pieces or chips and fry them. The smooth, creamy texture goes with a variety of meats, nuts, and beans.
You can substitute sweet potatoes, yams, or regular baking potatoes such as russets for boniatos.
http://www.foodreference.com/html/tboniatocubanswpot.html
http://sarasota.extension.ufl.edu/FCS/FlaFoodFare/Boniato.htm