Pierce broccoli package and place on paper plate.
Microwave at HIGH 5 to 6 minutes.
Drain well and set aside.
Microwave butter in a 2-quart casserole at HIGH 30 seconds to melt.
Stir in onion.
Cover with plastic wrap and microwave at HIGH 5 to 6 minutes.
Stir well after 3 minutes.
Add soup, mushrooms, cheese spread, and hot sauce.
Cover with plastic wrap and microwave at MEDIUM-HIGH 5 to 6 minutes or until cheese melts.
Stir in cooked broccoli and salt.