Melt the butter in a large soup pot over medium-high heat, tilting the pot occasionally for even coating, until fragrant.

Add chopped onion and minced garlic, stirring frequently until the onion is translucent (about 4-5 minutes).

Crumble in ground Italian sausage and cook until browned (about 6-8 minutes).

Pour in chicken bone broth and fire-roasted tomatoes, stirring well, then add cream cheese and stir until melted and smooth (about 3-5 minutes).

Mix in diced zucchini, dried basil, oregano, and black pepper. Bring to a gentle boil, then reduce heat and simmer uncovered for 15-20 minutes.

Stir in baby spinach and cook until wilted (about 3 minutes).

Ladle soup into bowls and top with shredded Parmesan cheese before serving.