1. In a saucepan, bring the water to the boil. Stir in the barley. Reduce heat, cover and simmer 30 minutes.
2. Cook pasta according to package instructions; drain.
3. In a food processor, finely chop the coriander, spring onions and half of the tomatoes. Mix in the stock and Parmesan cheese and process until well blended.
4. In a large bowl, toss the barley, pasta, coriander mixture, remaining tomatoes and rocket. Season with salt and pepper and serve immediately.