Preheat the oven to 200C/400F/Gas 6. Grease an ovenproof dish with a little sunflower oil.
In a bowl, mix together the asparagus, spring onion and peas. Stir in the mint leaves and parmesan until well combined.
Tip the beaten eggs into the bowl and mix carefully. Season with freshly ground black pepper and mix again.
Spoon the frittata mixture into the prepared ovenproof dish. Place the dish onto a baking tray, then transfer to the oven and bake for 15-20 minutes, or until the eggs have completely set and a skewer inserted into the centre of the frittata comes out clean.