• Preheat oven to 375F

Lasagna noodles

• Bring a large pot of water to a boil. Add noodles and salt, and cook to al dente, according to package instructions. Rinse noodles well under cold water.

Sauce

• Shred veggies in food processor while heating up a large frying pan.
• Cook carrot, celery, and onion until softened (approx. 3-5 minutes).
• Add garlic and cook until fragrant (about 30 seconds).
• Add ground beef and cook until no longer pink.
• Add mushrooms and remove from heat.
• Add spinach and stir.
• Add prepared sauce.

Cheese mixture

• Combine beaten egg, cheese, and diced spinach in a medium bowl. Divide into quarters.

Assemble rolled lasagna

• Cover the bottom of casserole pan with a thin layer of sauce.
• Lay 3 noodles out flat on a cutting board. Evenly spread 1/4 of the cheese mixture between the three noodles (about 1/4 cup each). Top with sauce (~3-4 tablespoons). Roll up tightly and place in pan, seam down.
• Repeat for remaining 9 noodles.
• Spread remaining sauce over rolls. Sprinkle with 1½ cups shredded mozzarella.

Bake

• Cover the pan with tinfoil and bake for 45 minutes.
• Uncover and bake another 5-10 minutes until the cheese begins to brown.
• Let cool for 15-20 minutes before serving.