Thaw the broccoli. Easiest is to thaw one package at a time in the microwave it at 2/3 the time on the package. Drain the thawed broccoli and set it aside.
Add the garlic to the mushroom soup and heat it. Add half the cheese to the mixture. Heat again until the cheese is melted. Add the rest of the cheese to the mixture and heat again until all the cheese is melted.
Put the thawed florets in a baking dish and add the mixture. Heat in a 400° oven until the casserole just starts to brown (about 20 minutes).
Serve and enjoy!