In a large skillet over high heat, add oil. Add the onions and carrots, season with 1/2 tsp each of salt & pepper, and sauté for about 5 minutes, until beginning to soften. Push the veggies to the edges of the pan, add the sausage to the center, and sear for 1 minute on each side. Crumble and cook until deeply browned. Stir in the garlic and tomato paste and cook, stirring constantly, for 1 minute. Transfer everything to a 6-quart slow cooker.
Add marinara sauce, crushed tomatoes, chicken broth, sugar, basil, oregano, parsley, and bay leaf. Stir to combine.
Cover and cook on LOW for 5–7 hours or HIGH for 3–5 hours.
About 30–40 minutes before serving, break lasagna into bite-size pieces and add them to the crockpot. Stir, cover, and cook on HIGH for 25–35 minutes, or until tender. Add extra broth if the soup thickens too much.
Remove the bay leaf. Stir in the heavy cream, if using. Taste and adjust the seasoning. Add a splash of balsamic vinegar if you’d like a little acidity.
In a small bowl, stir together ricotta, mozzarella, and Parmesan.
Ladle hot soup into bowls. Top each with a big scoop of the cheese mixture and garnish with fresh basil. Enjoy!
Notes
Note 1: I grab a block of Parmesan and grate it with a microplane for the best texture!Storage: Since the pasta will keep soaking up broth, use a wire skimmer to strain it out and store separately.