Bring a large pot of water to a boil over high heat. Add pasta, stir, reduce heat to medium-high, and simmer until al-dente, about 7-8 minutes. Add oil to water if desired to avoid the pasta from sticking.
While the pasta is cooking, in a medium-sized skillet, over medium-high heat, add oil, onion, and garlic. Sauté for about 2-3 minutes, until the onions start to become tender.
Add chorizo, paprika, chipotle honey rub, and sage. Sauté for about 5-6 minutes, stirring occasionally until the meat is cooked through.
Drain cooked pasta and return to the same pot it was cooked in. Dump in the chorizo mixture, beans, buttermilk, tomato paste, chipotle peppers, salt, black pepper, and spinach.
Stir pasta mixture until the spinach begins to wilt, but remains bright green in color. If the spinach does not begin to wilt after about 1-2 minutes, return the pot to medium-low heat for a minute or two and stir, until the spinach wilts.