No-boil lasagna noodles are perfect for this recipe, as they absorb all the juices that accumulate in the crockpot. Use 2 (10-ounce) packages of frozen chopped spinach in place of fresh, if you prefer. Also, any mushroom will work.
4 cups torn spinach
2 cups sliced cremini mushrooms
1/2 cup commercial pesto
3/4 cup (3 ounces) shredded part-skim mozzarella cheese
3/4 cup (3 ounces) shredded provolone cheese
1 (15-ounce) carton fat-free ricotta cheese
1 large egg, lightly beaten
3/4 cup (3 ounces) grated fresh Parmesan cheese, divided
1 (25.5-ounce) bottle fat-free tomato-basil pasta sauce
Arrange the spinach in a vegetable steamer; steam, covered, 3 minutes or until spinach wilts. Drain, squeeze dry, and coarsely chop. Combine spinach, mushrooms, and pesto in a medium bowl, stirring to combine; set aside.
Combine mozzarella, provolone, ricotta, and beaten egg in a medium bowl, stirring well to combine. Stir in 1/4 cup Parmesan, and set aside. Combine the pasta sauce and the tomato sauce in a medium bowl.
Spread 1 cup pasta sauce mixture in the bottom of a 6-quart oval electric slow cooker coated with cooking spray. Arrange 3 noodles over pasta sauce mixture; top with 1 cup cheese mixture and 1 cup spinach mixture. Repeat the layers, ending with spinach mixture. Arrange 3 noodles over spinach mixture; top with remaining 1 cup cheese mixture and 1 cup pasta sauce mixture. Place remaining 3 noodles over sauce mixture; spread remaining sauce mixture over noodles. Sprinkle with the remaining 1/2 cup Parmesan. Cover with lid; cook on LOW 5 hours or until done.