Place parsley, basil, chilli and garlic with oil in a food processor and blend until lightly chopped. Transfer half the mixture to a mixing bowl. Add prawns and toss to coat thoroughly. Cover with plastic wrap and allow to marinate for 30 minutes.
Meanwhile, preheat oven to 200 °C (400 °F).
Transfer remaining herb mixture to a shallow microwave-proof dish. Add tomatoes, beans, asparagus and snow peas and toss to combine. Cover with plastic wrap and microwave on high for three minutes, or until vegetables are just cooked. Set aside and allow to cool slightly.
Transfer prawns to a baking tray and bake for ten minutes, or until cooked. Remove from oven and tip prawns and cooking juices into cooling vegetables. Add mixed greens and toss to combine.
To serve, squeeze over lemon juice and season with pepper.