Step 1

Preheat oven to 350℉. Coat a 9-by-13-inch baking dish with cooking spray. Bring a large pot of water to a boil.

Step 2

Cook spaghetti according to package directions until al dente; drain and transfer to a large bowl; let cool slightly, about 10 minutes.

Step 3

Meanwhile, heat 1 tablespoon oil in a large nonstick skillet over medium heat. Add ground beef; cook, stirring and breaking up the beef with a wooden spoon, until no longer pink, about 6 minutes. Stir in Italian seasoning, salt, crushed red pepper and pepper; cook, undisturbed, until fragrant, about 1 minute. Use a slotted spoon to transfer the mixture to a medium bowl. (Do not wipe the pan.)

Step 4

Add the remaining 1 tablespoon oil to the pan and heat over medium heat. Add onion; cook, stirring occasionally, until soft and translucent, about 2 minutes. Add mushrooms and garlic; cook, stirring occasionally, until fragrant, about 5 minutes. Add spinach; cook, tossing often with tongs, until wilted, about 2 minutes. Stir in marinara sauce and the reserved ground beef mixture. Bring to a simmer over medium heat; simmer, undisturbed, until slightly reduced, about 5 minutes.

Step 5

Whisk eggs, ricotta and 1/4 cup each mozzarella and Parmesan in a large bowl. Add the spaghetti and toss until coated.

Step 6

Stir the marinara mixture into the spaghetti mixture, tossing until completely coated. Transfer to the prepared baking dish and top with the remaining 1/4 cup each mozzarella and Parmesan. Bake until the cheeses are melted and the pasta is warmed through, about 20 minutes. Let stand for 10 minutes. Garnish with basil, if desired.