1

Spray a large nonstick skillet with nonstick spray and set over medium heat. Add mushrooms and cook, stirring, until their liquid is released and almost evaporated, about 6 minutes. Add spinach in batches. Sprinkle with 1/4 tsp salt. With a slotted spoon, transfer spinach mixture to a bowl. Discard liquid.

2

Spray same skillet with nonstick spray and set over medium heat. Add beef, onion, and garlic and cook, breaking up meat with a wooden spoon until no longer pink, about 5 minutes. Stir in crushed tomatoes, tomato sauce, oregano, red pepper flakes, and remaining 1/2 tsp salt. Simmer 5 minutes.

3

Meanwhile, in a medium bowl, stir together ricotta, 3/4 cup mozzarella, 2 tbsp Parmesan, and 1/4 cup basil.

4

In bottom of a 6-qt slow cooker, spread one-third of beef mixture. Break 3 lasagna noodles in half and arrange over beef, breaking to fit as needed. Scatter one-third of mushroom mixture over noodles and top with half of ricotta mixture. Spoon half of remaining beef on top; break remaining 3 noodles in half and arrange on top of beef. Top with remaining mushrooms, ricotta, beef, and mushrooms.

5

Cover and cook until noodles are tender when pierced with a knife, 3 to 4 hours on Low. Uncover and turn off slow cooker. Sprinkle remaining 3/4 cup mozzarella and 3 tbsp Parmesan over lasagna. Cover and set aside until cheese is melted, about 10 minutes. Sprinkle with remaining 1/4 cup basil. Cut into 8 portions.