Vegetarian lasagna with spinach

Ingredients:

• 2 tbsp extra virgin olive oil
• 2 tablespoons butter
• 2 cloves garlic, chopped
• 2 cans of San Marzano tomatoes (800g each)
• 2 cups passata or tomato sauce
• A handful of torn fresh basil leaves
• 1 small onion, peeled and cut in half
• 2 packages frozen spinach, thawed and squeezed out of water
• 700 g mozzarella, thinly sliced, cubed, or coarsely grated
• 3 cups fresh ricotta (cow's or sheep's milk), drained
• 2 tbsp. grated parmesan or pecorino
• 2 large egg yolks, lightly beaten
• Freshly grated nutmeg, to taste
• 1 package no-cook lasagna, such as Barilla, or 12 regular lasagna noodles

Preparation:

1. Heat the olive oil in a saucepan and add the butter. Add the garlic and cook, stirring, for 2 minutes. Add the tomatoes and crush them slightly. Add the passata, a handful of torn basil leaves, the onion, and a pinch of salt and black pepper. Bring to a boil and simmer for 40-45 minutes. Remove the onion and set the sauce aside.
2. Separate the spinach into a bowl. Add half the mozzarella, the ricotta, 1.5 cups of Parmesan, and the egg yolks and stir. Sprinkle with grated nutmeg, salt, and pepper.
3. Spoon some sauce into a lasagna dish and top with three flat or four wavy lasagna noodles. Top with more sauce, then half the spinach and cheese mixture. Repeat the layers, finishing with noodles. Drizzle with a little more sauce and sprinkle with the remaining mozzarella and Parmesan.
4. At this point, you can refrigerate the lasagna if you're making it ahead. Bring to room temperature and bake at 190°C (350°F), uncovered, until done, golden brown, and bubbly, 60-70 minutes. Reheat the finished lasagna at 190°C (350°F), covered, for 40-45 minutes.
5. Let the lasagna rest for 20 minutes before slicing. Serve with the remaining sauce.