Step 1: Heat olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Add ground beef and Italian sausage (if using); cook, breaking meat apart, until browned and cooked through, about 8-10 minutes. Drain any excess fat.
Step 2: Add chopped onion to the pot. Sauté for 5-7 minutes until softened. Add minced garlic and cook for 1 minute until fragrant.
Step 3: Stir in tomato paste and cook for 2 minutes, stirring constantly. Pour in crushed tomatoes, marinara sauce, beef broth, and water. Add dried basil, oregano, red pepper flakes (if using), salt, and black pepper. Bring to a simmer.
Step 4: Break lasagna noodles into 1-2 inch pieces and add them to the pot. Stir well to submerge. Reduce heat to medium-low, cover, and simmer for 15-20 minutes, or until noodles are tender, stirring occasionally to prevent sticking.
Step 5: While soup simmers, prepare the ricotta dollop. In a small bowl, combine ricotta cheese, grated Parmesan, fresh parsley, garlic powder, salt, and black pepper. Mix until well combined and creamy.
Step 6: Taste the soup and adjust seasonings as needed. If too thick, add a little more broth or water. Stir in fresh spinach (if using) and cook for 1-2 minutes until wilted.
Step 7: Ladle hot Lasagna Soup with Ricotta Dollop into bowls. Top each serving with a generous dollop of herbed ricotta mixture. Garnish with extra fresh parsley or Parmesan. Serve immediately.