Bring a large saucepan of salted water to the boil. Add the risoni and cook following packet directions or until al dente. Drain and transfer to a large bowl.
Meanwhile, to make the dressing, combine all ingredients in a screw-top jar and shake until well combined. Pour half the dressing over the warm risoni, season with salt and pepper and stir until well coated. Set aside for 15 minutes to cool to room temperature.
Add the tomatoes, prawns, feta, pine nuts, parsley, chives and remaining dressing. Toss gently and serve.