Step 1: In a large pot or Dutch oven, brown the Italian sausage over medium-high heat, breaking it apart with a spoon as it cooks. Cook until no longer pink, about 5-7 minutes. Drain any excess grease.
Step 2: Add the diced onion to the pot with the sausage and cook until softened, about 5 minutes. Stir in the minced garlic and cook for another minute until fragrant.
Step 3: Pour in the chicken broth, scraping up any browned bits from the bottom of the pot. Bring the mixture to a boil.
Step 4: Add the ditalini pasta and cook according to package directions (usually 7-9 minutes) until the pasta is al dente.
Step 5: Reduce the heat to low. Stir in the heavy cream and 1/2 cup of grated Parmesan cheese. Heat gently, stirring constantly, until the cheese is melted and the soup is warmed through. Do not let the soup boil after adding the cream.
Step 6: Season with salt, black pepper, and optional red pepper flakes to taste. Serve hot, garnished with fresh parsley or basil and additional Parmesan cheese, if desired.