Heat olive oil in a large deep skillet over medium heat.
Add chopped onion and cook until softened, about 3 minutes.
Add minced garlic and cook for 1 minute until fragrant.
Add ground beef to the skillet and cook, breaking it up with a spoon, until browned and cooked through, about 6-8 minutes.
Drain excess fat from the skillet if necessary.
Stir in marinara sauce, dried Italian seasoning, salt, and black pepper. Bring to a simmer.
Add broken lasagna noodles and water to the skillet, stirring to combine.
Cover the skillet and cook over medium-low heat for 15 minutes, stirring occasionally, until noodles are tender.
While noodles cook, in a small bowl, combine ricotta cheese, egg, half of the Parmesan cheese, and half of the chopped parsley. Mix well.
Remove the skillet from heat. Drop spoonfuls of the ricotta mixture evenly over the noodles and sauce.
Sprinkle 1 cup of shredded mozzarella cheese and the remaining Parmesan cheese evenly over the top.
Cover the skillet again and let it sit for 5 minutes to allow the cheese to melt.
Sprinkle the remaining 1 cup mozzarella cheese and remaining parsley on top before serving.
Serve hot, garnished with extra parsley if desired.