In a large pot or Dutch oven over medium heat, add the Italian sausage and diced yellow onion. Cook until the sausage is browned and fully cooked, breaking it apart as it cooks. Add the minced garlic and sauté for another 30–60 seconds until fragrant. Carefully drain any excess grease from the pot.
Pour in the marinara sauce, petite diced tomatoes, and chicken broth. Stir everything together until well combined.
Add the onion powder, garlic powder, Italian seasoning, salt, black pepper, a pinch of sugar, and bay leaves. Stir well and bring the mixture to a gentle simmer.
Remove and discard the bay leaves. Pour in the heavy cream and stir until fully incorporated into the tomato sauce.
Add the uncooked ditalini pasta directly into the pot. Stir and bring the mixture to a gentle boil. Cook according to the pasta package directions, stirring occasionally to prevent sticking, until the pasta is al dente.
Once the pasta is tender, reduce the heat to low. Stir in the grated Parmesan and shredded mozzarella cheese until melted and the sauce is creamy.
Remove from heat and allow the pasta to sit for a few minutes to thicken. Serve warm with additional Parmesan cheese if desired and enjoy!