Vegetarian Lasagne Super Stretchy

Method

1. Cut the red onion in half, then slice thinly.
2. Peel and trim the carrots, cut into thin slices then into 2-3 cm sticks.
3. Cut the zucchini in the same way.
4. Clean the mushrooms by removing the earthy part of the stem and wiping with a damp cloth, then slice.
5. In a pan, heat a drizzle of oil and sauté the onion over high heat for 5–6 minutes until soft and lightly caramelized.
6. Add the carrots, zucchini, and mushrooms, season with salt, and cook over high heat for 5 minutes.
7. Add the tomato passata, stir, cover, and cook for 15 minutes, stirring occasionally.
8. Add the spinach in two batches, stirring to wilt.
9. Adjust seasoning with salt.
10. Prepare the baking dish: spread a thin layer of béchamel on the bottom.
11. Cover with a first layer of lasagna sheets, trimming the corners if the dish is rounded.
12. Add more béchamel, then the vegetables, slices of melting cheese, and grated cheese.
13. Repeat for 5 layers.
14. For the last layer, cover the vegetables with béchamel, omit the sliced cheese, and add extra grated cheese to form a crust.
15. Bake at 180°C (350°F) for about 35 minutes. Optionally, add a couple of minutes under the broiler.
16. Serve.