To a dry skillet over medium heat, add the fennel seeds. Toss and stir the seeds often until they are fragrant and just begin to get some browning from the pan. Immediately remove them and set aside.
1 teaspoon fennel seeds
Add the sausage to the skillet and cook over medium heat until the sausage is completely cooked through. This should take about 8-10 minutes. Remove the sausage from the pan to a paper towel-lined plate to drain excess grease. Leave 1 teaspoon of grease from the sausage in the pan.
1 pound mild or sweet Italian sausage
Heat the skillet over medium heat and add the onion, bell pepper, and celery. Sauté briefly until the onion just starts to become translucent on the edges.
1 medium yellow onion, 1 medium red bell pepper, 1 large stalk of celery
Add all the ingredients, including the cooked sausage, toasted fennel seeds and sautéed veggies, into the pot and bring to a boil. Turn the heat down to a simmer and cook the soup for 30 minutes. Taste for seasonings and add more salt if necessary.
2 cans (15.5 oz each), 6 cups unsalted chicken stock (48 ounces), 1 teaspoon kosher salt and more to taste if needed, ½ teaspoon black pepper, 1 teaspoon balsamic vinegar
Serve topped with freshly grated parmigiano-reggiano (Parmesan cheese), a sprinkle of crushed red pepper flakes for a little heat and some crusty bread!
Parmesan cheese for serving