Place a large pot or Dutch oven over medium heat. Add the sausage and cook, using a wooden spoon to break it up into small pieces, until it begins to brown.

Add the diced onion and green bell pepper. Cook, stirring occasionally, until the vegetables are softened and the sausage is fully browned.

Stir in the minced garlic, Italian seasoning, and crushed red pepper. Cook for about 1 minute, just until fragrant.

Carefully drain excess grease from the pot if needed.

Slowly pour in the chicken broth, scraping up any browned bits from the bottom of the pot as you stir.

Add the crushed tomatoes, pizza sauce, and quartered pepperoni (reserving some for garnish). Stir to combine, and bring the soup to a simmer, about 3 to 5 minutes.

Reduce the heat to low. Stir in the shredded parmesan cheese until fully melted. Taste, and season with kosher salt if needed.

Ladle into bowls and garnish with fresh basil, extra shredded parmesan, and reserved pepperoni. Serve warm.