Preheat oven to 350 degrees
In a large pot, brown the ground beef and drain. Remove to a bowl and set aside.
Add olive oil to pan and sauté the mushrooms for several minutes or until nicely browned. Add garlic and stir 20 seconds.
Add tomato sauce, tomato paste, spinach, sea salt, pepper, and oregano to the pot.
Stir well and bring sauce to a boil. Turn the heat down and simmer for 5-10 minutes. (take the lasagna sheets out of the freezer at this time-they only need just a few minutes to thaw- too long and they will turn to mush).After the sauce has simmered, use an immersion blender to hide you the vegetables from your kids.:) Add ground beef back into sauce. In a 9x13 pan, spread a layer of sauce on the bottom. If you skip this step, these lasagna noodles will get extra crispy and no one wants that!
Next add a layer of lasagna sheets, mozzarella cheese, and sauce.
Repeat this last step, but remember to rotate your sheets so they are perpendicular to the first layer. And then again, placing your sheets the same direction as the first layer. You should have three layers of sheets, mozzarella, and sauce. Top with shredded parmesan cheese.
Cover with foil and bake at 350 degrees for 25 minutes-do not bake 40 minutes like the lasagna sheets box says! Lasagna is done when all the cheese on top is melted and the edges are bubbling.
Serve with a yummy summer salad. Then sit down and enjoy family time around the table.