Cook the sweet potato in a steamer basket over a saucepan of simmering water for 10-12 minutes or until tender enough to mash. (Alternatively, place in a microwave-safe bowl, cover with 2 layers of plastic wrap and microwave on High for 10 minutes or until tender. Drain if necessary.) Transfer to a heatproof bowl. Set aside to cool slightly.
Use a potato masher to mash the sweet potato until smooth. Stir in the salami, cheddar and pizza sauce until combined. Roll level tablespoonfuls of the mixture into balls. Place on a tray lined with baking paper.
Place the flour, egg and breadcrumbs in separate shallow bowls. Roll the balls in flour, dip in egg and then roll in breadcrumbs to coat. Return to the prepared tray.
Add enough oil to a large frying pan to reach a depth of about 1cm. Heat over medium-high heat. Working in batches, shallow-fry the balls, turning often, for 5 minutes or until crisp and golden. Transfer to a plate lined with paper towel to drain. Serve with pesto, if you like.