Melt butter in a large stock pot over medium heat. Add onions and sauté until soft. Add mixed vegetables, broth, kidney beans, tomatoes, spinach, and tomato paste; simmer gently for 1 1/2 hours.

Use a slotted spoon to transfer about 1/2 of the vegetables to a blender or food processor, reserving the liquid in the stockpot. Purée vegetables until smooth, then return to the pot.

Stir in heavy cream, macaroni, garbanzo beans, 1/2 of the Parmesan cheese, garlic powder, parsley, pepper, basil, and salt. Cook, stirring frequently, for 30 minutes.

Ladle into bowls and sprinkle with remaining Parmesan cheese.