Preheat the oven to 180°C/350°F/gas 4.
Place the pitta pieces on a baking tray, lightly drizzle with olive oil and toss to coat. Bake for 8-10 minutes or until slightly crisp and lightly golden. The idea is to dry out the bread without burning it. Remove and set aside to cool.
Place the lettuce, onion, tomatoes, cucumber, radishes and herbs in a large bowl and toss to combine.
To make the dressing, put all of the ingredients into a small bowl and season. Whisk until well combined and emulsified.
Just before serving, add the pitta croutons to the salad, drizzle over the dressing and toss to coat. Serve immediately.