How to Make It
Put the sweet potatoes in a medium saucepan, cover with water and bring to a boil. Add a large pinch of salt and simmer over moderately high heat until tender, about 20 minutes. Drain the sweet potatoes and return them to the pan. Shake the pan over high heat to dry out the potatoes, about 1 minute.
Mash the potatoes until smooth. Stir in the cornstarch, sugar, cinnamon, allspice and Cheddar. Season with salt.
Put the sesame seeds in a shallow bowl. Using your hands, roll the sweet potato mixture into 1-inch balls. Roll the balls in the sesame seeds until coated.
In each of 2 large skillets, heat 1/4 inch of oil. Add the sweet potato balls and fry over moderate heat until golden brown all over, about 1 minute per side. Drain on paper towels and serve warm or at room temperature.