In a large Dutch oven, brown the Italian sausage over medium-high heat. Use a wooden spoon to break it into small crumbles. If the sausage is very fatty, drain all but one tablespoon of the rendered fat.
Add the diced onion to the pot and sauté until translucent. Stir in the minced garlic, basil, oregano, and red pepper flakes.
Add the tomato paste to the center of the pot. Stir it into the meat and onions for 2 minutes until it turns a dark rust color. This "toasting" of the paste removes the metallic canned taste and adds incredible depth.
Pour in the crushed tomatoes and the bone broth. Bring the mixture to a rolling boil, then reduce heat to medium-low.
Add the broken lasagna noodle shards directly into the soup. Cook, stirring occasionally to prevent the noodles from sticking together, for about 12–15 minutes or until the pasta is al dente.
While the pasta cooks, stir together the ricotta, mozzarella, Parmesan, and parsley in a small bowl.
Ladle the hot soup into deep bowls. Place a generous dollop of the cold cheese mixture right in the center of each bowl. As you eat, the cheese will melt into the broth, creating that signature lasagna creaminess.