Bring a large pot of water to a boil. Add the whole sweet potato and cook for about 15 minutes. You want it to be slightly softened, but not easily mashed - you will need to be able to grate it. Drain and let it sit until cool enough to handle, then grate with a cheese grater.

Combine the shredded potato and egg in a medium bowl and use a fork to combine. In another bowl, combine the flour, salt, paprika and garlic powder. Add the flour mixture to the potato and stir to combine.

Pour the oil into a deep fryer or in to a heavy pot. Heat the oil until it is 375ºF. Place a few sheets of paper towels on a plate to drain the tots when they are done cooking.

Form the potato mixture into 1-inch balls** and add to the hot oil, being careful not to overcrowd the pot. (It will take you several batches to cook all of the potato mixture.) Fry for 3 minutes, then remove with a slotted spoon and drain on the paper-towel lined plate. Repeat with the remaining batter, allowing the oil to come back to temperature between batches.

In a small bowl, combine the yogurt and the ketchup. Serve with the hot tots.