1Brown the sliced onions I one tablespoon of oil,set to the side,next brown the mushrooms in the other tablespoon of oil and add to the onions. Season with the salt and pepper.
In a large mixing bowl combine the mushroom mixture with the beaten eggs,milk or half and half,all of the cheeses and the thyme. Add the crumbled bacon to the mix.Add the spinach to the mix.
2Butter a three quart baking dish and fold in the batter,spread it out evenly and cover with plastic wrap. Refrigerate for four hours.
3Heat your oven to 350 degree and bake uncovered for fifty minutes. If it start to brown too much cover it with foil,cook until egg is set. Uncover and serve right away or at room temperature. Can be served with your choice of side or as itself! Enjoy!:)
4Please note that the prep time is four hours long to allow for the casserole to set in the refrigerator.