Incorporate the Italian seasoning, salt, black pepper, sage, paprika, and cayenne pepper. Add the fresh spinach and parsley, cooking until the spinach wilts, about 1 minute. Sprinkle in the flour and stir, ensuring it coats the vegetables and absorbs the butter and seasonings; continue to cook, stirring constantly, for an additional 2 minutes. Add the frozen mixed vegetables and vegetable broth; bring to a simmer. Cook until the mixture thickens slightly, around 3 to 4 minutes. Remove from heat and stir in the nutritional yeast.