Bring a large saucepan of water to the boil. Add the pasta and cook according to pack instructions. For al dente pasta, reduce the cooking time by 2-3 minutes. Add the broccoli 5 minutes before the end of cooking time.
Meanwhile, to make the dressing, place the watercress, almonds, garlic, Parmesan and olive oil in a food processor. Whiz to combine.
Drain the pasta and broccoli and place in a large serving dish. Pour over the dressing and toss through to coat the pasta and broccoli. Sprinkle over the remaining Pamesan and season with salt and pepper.