The Yacón is a species of daisy traditionally grown in the Andes for its lightly sweet and crisp tuberous root. It's a relative of sunchokes and sunflowers. Yacón is also known as the Peruvian Ground Apple. It's similar to Jicama in both flavor and crispy texture, but has an added layer of floral sweetness due to inulin, a naturally occurring polysaccharide. Yacón is mostly made up of water and fructooligosaccharides (similar to Blue Agave), which taste sweet, but aren't metabolized, and thus are very low-calorie.
The tuber, when raw, has a texture like a water chestnut, making it a great, mildly-sweet addition to a salad or a crudités platter. To prepare them raw, peel them and top them with lemon juice to prevent browning. They are occasionally boiled and then peeled, which makes them sweeter, and turns them into a potato-y texture, but a bit waxier.
Note: these tubers aren't always the prettiest. They may have some slight cracks or scarring, but once peeled, the white flesh should be delicious.