Preheat oven to 400 degrees F. Combine the first five ingredients in a small skillet. Set over medium heat and cook just until the butter melts; remove from the heat. Roll each sole fillet into a loose cylinder and place in a shallow baking dish. Scatter the prawns around the baking dish. Spoon the butter mixture over the sole and prawns; season with salt and pepper. Bake for 12 to 15 minutes, or until just cooked through. Divide among 4 plates, spoon the pan juices over top, sprinkle with parsley and serve.