Sauté 1 medium onion, 1 rib celery, 3 cloves garlic (all chopped) in the extra virgin olive oil for 3 minutes.Add 2 tablespoons tomato paste, ½ teaspoon rosemary, 2 bay leaves, 8 ounce mushrooms (grated), 1 teaspoon salt, and ⅛ teaspoon black pepper and cook for 5 minutes.Add 1 cup dried lentils (rinsed), 4 cups vegetable broth, and 24 ounces tomato puree and simmer for about 30 minutes until the lentils are cooked.Fish out the herbs, stir in 3 tablespoons balsamic vinegar, then coarsely blend most of the sauce with an immersion blender. Taste and adjust for salt.
MAKE THE WHITE SAUCE
Melt 7 tablespoons (3½ ounces) butter in a saucepan. Remove from the heat and sift in ⅔ cups (3½ ounces) all-purpose flour. Whisk until combined, bring to medium heat and whisk 1 more minute.Pour 4 cups milk in while stirring and cook for 5 minutes. Stir often and aim for a creamy and pourable white sauce.Remove from heat and season with ½ teaspoon salt, 2 twists black pepper, and 1 pinch grated nutmeg.
ASSEMBLE THE LASAGNA
Preheat the oven to 350°F or 180°C.Spread a thin layer of white sauce on the bottom of a 9 x 13 inches / 20 x 30 cm casserole dish. Top with some lentil bolognese.Cover with a layer of lasagna noodles. Top the noodles with whitesauce, lentilbolognese, and a handful of grated parmesan.Repeat until you have 5 layers of pasta.The top layer should have more sauce and cheese. Keep this in mind as you build the lasagna.
BAKE THE LASAGNA
Bake the vegetarian lasagna for 30 minutes on a rack in the center of a preheated oven at 350°F or 180°C.Let it cool down for 10 minutes before slicing and serving it with plenty of fresh basil.
Nutritional information is an estimate for 1 portion of vegetarian lasagna out of 8 portions.NOODLESThere are three types of lasagna noodles:
No-boil ready-to-bake dry lasagna noodles: Recommended for hassle-free lasagna and beginner cooks. Find them in the dry pasta section of most supermarkets.
Fresh lasagna noodles: Not all supermarkets keep them, but they are an excellent choice if they do. Read instructions on how to use them; sometimes they need to be pre-boiled. Find them in the refrigerated section of larger supermarkets or Italian delis.
Dry lasagna noodles: Like regular pasta, they must be boiled in plenty of salted water before you can use them to make lasagna. This can get tricky if you are not an advanced cook and requires longer preparation than no-boil or fresh noodles.
SUBSTITUTIONSVegan: Substitute our vegan white sauce for the regular white sauce and a non-dairy cheese for the parmesan. The lentil bolognese is vegan and does not require any changes.Gluten-free: The lentil bolognese and the white sauce are naturally gluten-free. Substitute lasagna noodles for GF lasagna noodles.STORAGEMake ahead: This vegetable lasagna is ideal for meal preparation. You can prepare, freeze, and bake it from frozen when ready to serve.The baking time remains roughly the same, with an additional 5 minutes.Alternatively, you can assemble the lasagna, cover it, refrigerate it, and bake it within 12-16 hours.Refrigerator: Store leftover lasagna in the same casserole dish, wrapped in plastic, or transfer to an airtight container. It will keep for up to 4 days.Freezer: For best results, freeze the lasagna before baking. When ready to eat, bake from frozen for 20 minutes covered with aluminum foil, then uncover and bake for an additional 10-15 minutes.Reheating: Warm up vegetable lasagna using an air fryer, oven, or microwave.