Start by heating a large pot over medium heat. Add the Italian sausage and cook it until browned, which usually takes about 5-7 minutes. Make sure to crumble the sausage as it cooks for even browning.

Add in the diced onion and minced garlic to the pot, stirring them into the sausage. Sauté for an additional 2-3 minutes until the onion is translucent.

Next, toss in the sliced carrots and celery, cooking for another 4-5 minutes until they soften slightly.

Pour in the diced tomatoes along with their juices and the chicken broth. Stir well, then add the cannellini beans, Italian seasoning, salt, and pepper.

Allow the soup to come to a gentle boil. Once boiling, reduce the heat to a simmer and let it cook for about 20 minutes.

In the last few minutes of cooking, add the fresh spinach, allowing it to wilt into the broth.

Taste and adjust seasoning if needed before serving hot.