Preheat the oven to 190°C/170°C. Place sweet potatoes on a baking tray and bake for 50-60 minutes or until tender (test with a pointed knife in the side). Remove from the oven and when cool enough to handle, cut in half horizontally. Scoop out the flesh, leaving about 1cm in the skin.
Mash the sweet potato flesh with a fork and add the corn, tuna and parsley. Stir in the eggs, and season to taste. Place the sweet potato shells onto an oven tray lined with non-stick baking paper. Spoon the mixture into the sweet potato shells (if the shells are very soft, prop the sides with a little folded foil).
Sprinkle cheese on top. Bake for 25 minutes until set and golden. Serve immediately with salad or steamed green vegetables.
Tips & Hints:
To get ahead, you can pre-roast the sweet potatoes up to 2 days ahead.