Dice the onion, carrot, celery, and red bell pepper. Mince the garlic. This will ensure even cooking and flavor distribution.

Remove the casings from the Italian sausage and break it into small pieces. This allows the sausage to cook evenly and integrate into the soup.

In a large pot, heat the olive oil over medium heat. Once hot, add the sausage pieces. Cook for about 5-7 minutes, stirring occasionally, until browned and cooked through. This step adds depth of flavor to the soup.

Add the diced onion, carrot, celery, and red bell pepper to the pot. Sauté for 5-7 minutes until the vegetables are softened. Stir frequently to prevent sticking.

Add the minced garlic and sauté for an additional 1-2 minutes until fragrant. Garlic burns easily, so keep an eye on it.

Stir in the diced tomatoes (with juices), chicken broth, cannellini beans, oregano, basil, red pepper flakes, salt, and black pepper. Bring the mixture to a boil.

Once boiling, reduce the heat to low and let the soup simmer for 20 minutes. This allows the flavors to meld together.

Ladle the soup into bowls and garnish with chopped parsley and grated parmesan cheese, if desired. Serve hot for a comforting meal.