1. Tomato Sauce: In a large saucepan, sauté a finely chopped onion with a little olive oil.
2. Then add the diced tomatoes, salt, and pepper.
3. Let simmer for about 2 hours over low heat, partially covering the saucepan.
4. Remember to stir occasionally and add vegetable broth as needed.
5. Béchamel Sauce: In a saucepan, melt butter. Add the flour once the butter is melted.
6. Gradually incorporate the milk and stir constantly to avoid lumps. When the mixture thickens, turn off the heat.
7. You can grate a little nutmeg over your preparation, add a pinch of salt and some pepper, and set aside.
8. Preheat your oven to 200°C (400°F).
9. Lasagna: Peel and chop the onion, carrot, and celery.
10. Place the vegetables in a pan and sauté them with a little olive oil.
11. Add the ground beef and minced garlic, and sauté over low heat.
12. Then add the red wine and cook over high heat to evaporate the alcohol.
13. Assemble your lasagna: béchamel, bolognese sauce, mozzarella slices...
Finish with mozzarella and Gran Padano cheese.
14. To finish your bolognese sauce, add the previously prepared tomato sauce to your ground meat mixture.
15. Place your dish in the oven for 40 minutes at 200°C (400°F).