Preheat oven to 375F.
Lightly spray a baking dish with cooking spray and set aside.
Pierce the sweet potatoes 6 times.
Place on a microwaveable plate and microwave for 6 minutes, rotating halfway through.
Remove from microwave oven and let stand several minutes.
Once cool enough to handle, cut them down the middle, lengthwise.
Scoop out the flesh, careful not to cut through the skins, and transfer to a medium mixing bowl.
Stir in the basil pesto; add grated parmesan, salt and fresh ground pepper and mix and stir until smooth and well incorporated.
Taste for seasonings and adjust accordingly.
Spoon the mixture back into the potato skins.
Transfer the potatoes to previously prepared baking sheet.
Bake for 15 minutes.
Remove from oven and add mozzarella cheese and pine nuts; continue to bake for 4 more minutes, or until cheese is melted.
Remove from oven and let stand couple minutes.
Transfer to serving plates and top with marinara sauce and chopped fresh parsley.