You can substitute 1 cup of mashed banana for the sweet potatoes; reduce the sugar to 1/2 cup and bake as directed.
Preheat oven to 400 degrees. Prick sweet potatoes all over with a fork; place on a parchment-lined baking sheet. Bake until tender when pierced with a knife, about 1 hour. Let cool, then scoop out and mash flesh; discard skins. Measure out 1 cup, reserving remainder for another use.
Reduce oven to 350 degrees. Line a standard 12-cup muffin tin with baking cups or lightly brush with oil. In a medium bowl, whisk together flour, baking powder, baking soda, cinnamon, and salt. In another bowl, whisk together sugar, eggs, oil, and mashed sweet potato. Stir wet ingredients into dry until just combined. Fold in chocolate.
Divide batter evenly among muffin cups. Bake until golden and tops spring back when lightly touched, about 24 minutes.Let cool 5 minutes in tin, then transfer to a wire rack and let cool completely.