Place a large pot of water over high heat. Bring to a boil before adding 2 Tablespoons of salt and holding at a boil until you are ready to cook the pasta.
Prepare the Swiss chard by washing thoroughly. Use a sharp knife to separate the stems from each leaf. The stems require more time to cook than the delicate leaves, so I like to add them to the pan separately. Chop the stems into ½ inch pieces. Roll the leaves and slice into thin ribbons.
In a large skillet over medium-high heat, add the olive oil, tilting the pan to cover the entire bottom surface with oil. Add the sausage that was removed from its casing, breaking it up into small pieces as it cooks. Cook until it has browned evenly, approximate 5-6 minutes. Add the garlic, red pepper flakes (if you desire a spicy pasta), and tomato paste. Stir to incorporate and allow to cook for 1-2 minutes.
Add the Swiss chard stems and sauté for 2-4 minutes, stirring occasionally to prevent it from sticking to the pan. Add the sliced leaves, salt and pepper, and half of the bone broth or stock, stirring to incorporate. Lower the heat to medium low and allow the mixture to simmer as you cook the pasta, adding more broth as needed to keep the pan from going dry.
Add the dried pasta to the boiling salted water and cook until al dente, according to package instructions, (approximately 12 minutes). Drain the pasta before transferring to the skillet with the sausage and Swiss chard mixture. Stir to incorporate, adding more bone broth if needed to coat the pasta. Taste and season as needed before serving hot with a sprinkling of grated Parmesan cheese.