Put half of the vegetable shortening into a lge. pot, heat; saute onions until light golden color. Add beans, carrots, parsley and saute. Add 10 c. of the stock. Cover pot and cook at a low boil until vegs. are tender (abt. 45 min.). Pass soup through strainer or blender, then return to the pot. In another smaller pot, heat remaining shortening, then slowly add flour, stirring until well blended. Add remaining hot broth and continue to stir until sauce thickens, then season with salt and pepper. Remove sauce from heat and swirl in butter. Return bean puree to heat, bring to a quick boil, then stir in the sauce. Mix well and serve hot, with croutons if desired. NOTE: If soup is too thick, thin it by adding more hot broth.