Bring a pot of water to a rapid boil. Boil the sweet potato until it is fork tender - about 15 minutes. Remove from the pot and let cool completely. Cut it in half lengthwise and use a melon baller to scoop out bite size pieces of sweet potato. Set aside and chill.
In a food processor, combine all the ingredients for the leche de tigre. Pulse until smooth then strain through a sieve over a small bowl. Reserve 2-3 tablespoons of the liquid. Cover and chill the pureed leche de tigre.
Cut the fish into bite size pieces. In a large bowl, stir in the sweet potato balls, corn, shallot, habanero and cilantro (or parsley). Pour the 2-3 tablespoons of reserved liquid plus half of the leche de tigre over the flounder mixture. Stir well to combine and let "cook" in the sauce for 5-8 minutes - until the fish is no longer opaque.
Use a slotted spoon to serve the ceviche. Garnish with the remaining leche de tigre and cilantro. Serve right away and enjoy!