In a large pot over medium heat, add the Italian sausage, chopped onion, and diced bell pepper. Cook for about 7-8 minutes, stirring occasionally, until the sausage is browned and the onions are translucent.

Stir in the pepperoni, minced garlic, Italian seasoning, and a pinch of red pepper flakes. Cook for an additional minute.

Add the tomato paste to the pot, stirring well to ensure all ingredients are evenly coated.

Next, pour in the chicken broth and add your short pasta. Increase the heat to bring the mixture to a vigorous boil. Reduce the heat to medium, cover the pot, and let it simmer for 10-12 minutes.

After about 10 minutes, check the pasta for al dente texture; add a splash of water if it appears too thick.

Remove the pot from heat and add the shredded mozzarella cheese. Stir gently until the cheese melts.

Top the pasta with remaining mozzarella and optional garnishes. Let sit for 1-2 minutes before serving.