Cut sweet potatoes in half lengthwise and place cut side down on small parchment paper lined baking sheet. Roast in 400F (200C) oven for about 30 minutes or until tender. Once it’s tender, scoop sweet potato flesh into a bowl and mash with a fork or potato masher. Let cool completely. Add cheese, cornstarch, salt and pepper and stir to combine well. (Dough will be soft)
Using a heaping tbsp (15 mL) of the mixture, roll into a ball and tuck 1 bocconcini into centre and reshape to make sure it is well covered. Repeat with remaining ingredients, to make about 16 cheese balls.
Place panko breadcrumbs into a shallow dish and roll each sweet potato all in it to coat, if desired.
In a deep small saucepan, make sure oil only comes half way up the pan. Heat oil over medium high heat to 325F (160C). Gently place a few sweet potato balls into oil and fry for about 1 minute or until golden brown. Remove with slotted spoon to paper towel lined plate and repeat with remaining balls.
Make-ahead: Cover and refrigerate for up to 2 days. Place sweet potato balls on a small baking sheet and warm through in a 350F (180C) oven for about 10 minutes.