Sometimes spelled couche-couche, this is a Cajun-Creole way of turning mush into a potion so soothing that it puts young and old to bed, as in coucher. In a delightful 1929 cook book called Mandy’s Favorite Louisiana Recipes, devised by Natalie Scott to honor all the cooking Mandys (whose names were sometimes Pearl, Mammy Lou, and Prosine and sometimes Tante Celeste and Tante Felicie), Mandy is quoted as saying her kush-kush is “g