Preheat the oven to 425F. Prep a 13 x 18 inch baking tray by greasing it using butter or non-stick spray. Layer parchment paper on top and grease the paper as well.
Add 6 cups of water and 1 tbsp of salt to a large pot and bring to a boil. Turn the heat down to medium and add the polenta. Whisk continuously at first, then occasionally for 10 minutes or until the polenta thickens.
Mix in the butter until incorporated.
Add the spinach and stir for 2 minutes, or until the spinach starts to wilt.
Remove the pot from heat and add half the parmesan.
Pour the polenta onto the greased baking sheet and smooth it evenly across the top. The goal is to have evenly cooked lasagna. Evenly spread ½ cup of parmesan on top.
Put the tray in the oven and cook for 15 minutes or until the polenta feels hardened and the cheese on top has melted.
Remove from oven and let it cool in the pan for an hour, or until it is completely cold. You could also put the pan in the fridge or freezer to speed up the process (but don’t let it freeze!).
To bake the actual lasagna, turn the oven heat to 400F and prep a 9 x 13 inch baking dish. Like before, you can use butter or non-stick cooking spray. Don’t use parchment this time.
Finely chop the parsley and basil before adding it in a mixing bowl with the ricotta, egg, pepper, nutmeg, and ½ tsp salt. Stir until everything is thoroughly mixed.
Use a large, sharp knife or a pizza cutter to cut the cooled polenta in half horizontally. Place one half on the bottom of the prepped baking dish. Don’t worry if it breaks, just cover the surface as best you can.
Spread half the ricotta mix evenly on top of the first layer. Spread half the marinara on top next, then cover with half the mozzarella.
Repeat the next layers the same: polenta, remaining ricotta, remaining marinara, and remaining mozzarella. Cover with the rest of the parmesan.
To protect your oven from spills, put the baking dish on a larger tray before placing it in the oven for 30 minutes. For a crispier top, after it’s done cooking, turn your oven to broil and let the cheese on top crisp for a couple minutes.
Take the dish out of the oven and let it sit for 15 minutes before serving. Enjoy!
Video Note: The video is making only 2 servings, not 8 servings.