Boil a small pot of water. Cook pasta according to package directions; drain.
Meanwhile, heat a medium-sized dutch oven over medium heat. Brown sausage, breaking it into bite-sized pieces, or smaller. Drain grease (or use paper towels to soak up grease), if desired.
Stir in pasta sauce, basil leaves or puree, water, and half-and-half. Cook until warm then reduce heat to low.
Add cooked pasta and season soup with salt and pepper to taste. Toss in the fresh spinach and simmer until wilted. Serve with grated Parmesan cheese, if desired.
Notes
Source: Adapted from Picky PalateYou're Gonna Bake It After Allbakeitafterall.com