Cook the broccoli and onion together until broccoli is tender. I did mine in the microwave on HIGH, covered, for about 8 minutes. Drain very well. Grease a large pie plate; add the cheese, ham and broccoli and mix. Beat the eggs, cream, mustard, salt and pepper well with a whisk. Pour evenly over the broccoli mixture. Bake at 350º 35-45 minutes until a knife inserted in center comes out clean. Let stand 10 minutes before cutting.