I've made several batches of this recipe for savory biscotti. They are a pleasant crunchy texture after baking and cooling. The next day, after being stored in an airtight container, they are no longer crunchy! They are made with eggs, whole milk, and butter, and I'm wondering if the fat in those ingredients is why they lose their crunchiness. I like the richness that the fat provides. Any recommendations on how to keep them crunchy?