Prep: 1. Preheat oven to 400. 2. Slice onions and mushrooms. Shred spinach. Grate cheese. Make: 1. Heat 1 tablespoon oil over medium heat. 2. Cook onions, stirring occasionally, until lightly golden, about 5 minutes. 3. Add mushrooms; cook, stirring, until tender, 6-8 minutes. 4. Add spinach in two batches, letting the first batch wilt slightly before adding the next; cook until spinach is wilted and mixture is dry, 2-3 minutes total. Season with salt and pepper. 5. Brush one side of tortillas with remaining tablespoon oil. 6. Place 4 tortillas, oiled sides down, on two baking sheets. 7. Layer each tortilla with cheese, spinach mixture, and more cheese, dividing evenly. 8. Top with the remaining 4 tortillas, oiled sides up, and lightly press to seal. 9. Bake until cheese has melted and tortillas are golden brown, turning once, about 10 minutes in. Serve: Cut quesadillas into quarters.
We love to serve these with salsa and sour cream. If you're not making these for a crowd you can just as easily fry each one individually in a skillet.