Bake clean and stemmed mushroom caps at 400 for 5-7 minutes on a greased baking sheet until they soften and release water. Remove any remnants inside cap with tip of spoon and pat inside dry.

Saute ham in a dry skillet, stirring occasionally, until it starts to brown a little, 3-4 minutes.

Place a layer of grated cheese in bottom of caps. Add ham and pineapple. Top with more cheese.

Return to 400 degree oven and bake for 15 minutes or until cheese has melted and mushrooms are heated through and golden. Garnish with green onions and any browned cheese bits left on the baking pan. Serve warm