1. Pre-heat the oven to 350 degrees.
2. Heat a but of oil or butter in a medium pan over medium heat.While pan is heating, remove stem/middle from each mushroom to form a medium-sized hole for stuffing.
3. Add onion to pan.
4. Sautee for about three minutes and then add garlic and sautee for a few minutes more. Make sure not to burn the garlic!
5. Add spinach to onion and garlic.
6. Sautee for a couple minutes, or until completely wilted.
7. Remove pan from heat. Stir in cream cheese until combined. Season mixture with a pinch of salt.
8. Add a few small crumbles of goat cheese to each mushroom cap. Top with a spoonful of onion/spinach mixture (enough so that cap looks full).Top each mushroom with a few more crumbles of cheese.
9. Bake for 15 minutes.Devour!