Preheat the oven to 325 degrees F (165 degrees C).
In a large bowl, cream together the butter and Xylitol until smooth. Beat in eggs one at a time, then stir in vanilla. Combine the flours/meal, baking soda, and salt; stir into the creamed mixture until just blended. Mix in the spent grain and quick oats, walnuts, and chocolate chips. Drop by heaping spoonfuls onto ungreased baking sheets.
Bake for 12 minutes in the preheated oven. Allow cookies to cool on baking sheet for 5 minutes before transferring to a wire rack to cool completely.