This cheesy casserole is comforting and luxurious.
Preheat oven to 350 degrees F.
In a large sauté pan, melt butter and add onion. Cook 3 to 4 minutes. Add the mushrooms and continue cooking for 5 minutes. Add the garlic and red pepper flakes for an additional minute. Stir in spinach, a little at a time, and cook until wilted. Set aside to slightly cool.
In a large bowl, mix together the cooked rice, eggs, milk, and mozzarella cheese. Stir in the cooled spinach and mushroom mixture. Season with salt and pepper and place into an 8×8 casserole dish. Top with parmesan cheese and bake for 30 minutes.