Clean and separate mushroom caps and stems.
Mince the stems and onions for the mixture. (Do this before cooking the sausage--it takes a while.)
Place drained mushroom caps in a 13" x 9" baking dish.
Cook the sausage. (Just before the sausage is finished cooking, add the garlic, mushroom stems, and minced onion.)
Drain any grease.
Add cream cheese to the sausage mixture and cook a little longer.
Melt butter, if not using squeeze butter, and put a little in each mushroom cap.
Add a little water to just cover the bottom of the baking dish.
Fill the mushrooms with the sausage mixture.
Drizzle a little more butter on top of the mushrooms.
Preheat oven to 350º.
Bake for 30-45 minutes, or until the tops are crusty and the mushrooms turn dark. ( I bake them for roughly 45 minutes.)