Preheat the oven to 375 degrees F.
For a recipe with this many ingredients, I recommend gathering everything and having them in place. It will make the process much smoother. After gathering the ingredients, chop and prep the vegetables.
Warm the olive oil in a large skillet over medium heat. Add the onion, cook for a few minutes, and then add the garlic followed by the broccoli. Cook for a few minutes until the broccoli starts to turn brighter green. Add the mushrooms and zucchini and cook for 5 to 7 more minutes until everything is tender and most of the moisture has been steamed off. Season with the salt, pepper, and red pepper flakes. Stir in the spinach and navy beans at the end, and cook for a couple more minutes until the spinach is wilted.
While the vegetables cook, bring a pot of salted water to boil. Boil the lasagna noodles according to package instructions. Make sure to follow the cooking time listed for when the noodles will be baked after boiling so you don't make them too soft. Drain the noodles and rinse them with water to prevent sticking. To make sure you make enough noodles, see how they fit in a 13x9 baking dish and make however many you need to fill each noodle layer.
Use the same pot to make the sauce. Melt the butter over medium heat, then whisk in the flour. Slowly pour in the milk, whisking as you do so. Add the seasonings: garlic and onion powders, parsley, basil, oregano, salt, and pepper. Cook over medium-low heat, stirring frequently, until the sauce begins to thicken. Remove the sauce from heat once it is thick and creamy. Stir in the ¼ cup of grated parmesan.
Now it's time to layer the lasagna. Spread about ½ cup of sauce on the bottom of a 13x9 baking dish. Next, add a layer of noodles. I used 3 noodles for each layer: 2 that I kept intact and 1 that I cut in half to fit the remaining area that needed to be covered. You may need more or less depending on the size of your noodles. On top of the noodles, spread about ¾ cup of ricotta cheese. Next, spoon half of the vegetable and bean filling (about 2 cups) on top. Sprinkle 1 cup of the mozzarella cheese and spread 1 cup of the sauce after that. Repeat the layering process like this: noodles, ¾ cup ricotta, the rest of the veggie and bean filling, 1 cup mozzarella, 1 cup sauce, noodles, ½ cup mozzarella, and ½ cup parmesan.
Transfer the assembled lasagna to the oven and bake on the center rack for 30 to 35 minutes until the cheese is bubbling. If you do not want the top to get too browned, you can feel free to cover the dish with foil for about half of the cooking time (either at the beginning or during the second half).
Let the lasagna sit for 10 to 20 minutes before slicing and serving. Enjoy!
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