Whisk eggs together with water. Add parmesan and finely chopped rosemary and a pinch of salt and whisk until corporated. Set aside.
Peel and thinly slice your sweet potato with a sharp knife or with a mandolin.
Cook the sweet potato slices for a couple of minutes. Once cooked, drain and set aside.
Fry the leeks in a small knob of butter on medium heat until softened.
Add the sweet potatoes, fry and toss around so the leeks and potato slices are mixed together.
Pour over egg mixture.
Cook on medium heat, and when the outer edges are cooked, gently with a spatula drag these edges towards the center. Repeat until the egg is almost cooked.
Turn on your grill in your oven and cook for a couple of minutes or until the top is slightly browned.
Remove from pan, cut into quarters and finish with a sprinkle of fresh rosemary.