Remove the sausage from casings and crumble it into a large soup pot. Begin cooking it over medium heat and add red pepper flakes, smoked paprika, onion, and garlic. Saute until the sausage is fully cooked and drain if necessary. Add the chicken broth and Italian seasoning, increase heat to high, and bring to a boil. Add diced potatoes, cover, and reduce to a simmer. Cook potatoes until tender.

While the potatoes are cooking, place the milk, cream cheese, flour, and salt in a blender. Blend until smooth. Heat the butter over medium-low heat in a small saucepan, then add the milk mixture and cook over medium heat until thick (like a very thick cream soup or a stirrable pudding). When the potatoes are cooked, add the thickened milk mixture and chopped spinach. Season with additional crushed red pepper flakes and kosher salt to taste and serve with freshly grated Parmesan cheese. Serves 8-10.