Cook penne in a large saucepan of boiling, salted water according to packet directions. Add broccoli for last 4 minutes of cooking. Drain.
Meanwhile, melt half of butter in a saucepan on medium heat. Add flour and cayenne and cook, stirring, for 1 minute. Whisk in milk and cook for 4 minutes, stirring, until starting to boil and sauce thickens.
Combine penne, broccoli, white sauce, chicken and tasty cheese and season to taste. Spoon into a 10-cup ovenproof dish. Melt remaining butter and combine with parmesan and breadcrumbs. Sprinkle over pasta mixture. Place dish under a preheated hot grill for 2-3 minutes, until top is golden and crisp. Serve.