Preheat the oven to 350°F and line a baking tray with parchment paper. 

Arrange the sweet potato slices on the baking tray. Drizzle with olive oil, salt and pepper.

Roast sweet potatoes for about 20 minutes. Remove from the oven.

Heat 1 tablespoon of olive oil in an oven-safe frying pan. Add the roasted sweet potato slices, spinach and basil leaves. Cook gently on a low flame.

Beat the eggs well and season with salt and pepper to taste.  Mix in the shredded cheese and gently whisk together with the eggs.  Fry the eggs together with the vegetables on a low flame for five minutes.

Transfer into the oven and bake for about 10 minutes until the cheese is melted and the frittata is toasty.