Saute the Chopped Onions in a pan. When they are slightly cooked (Do not wait for them to become translucent as they will be baked again), add in the mushrooms.
Add the Salt and Pepper and the Italian seasonings, and cook the Mushrooms for a few minutes before adding the Spinach. Once the Spinach is cooked, drain any moisture the mushrooms or spinach might have given out.
Take it off the heat and cool for a few minutes. Layer the bottom of a baking dish with half of the cooked mushrooms and spinach.
Top this with another layer of half of the cheese. Add the rest of the spinach and mushrooms on top of this, and sprinkle the rest of the cheese on top of this.
Finally, garnish with the Parmesan and parsley before baking for an hour. Serve hot.
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