When you’ve got cookies that are a little too hard, whether from overbaking or age, lmoy suggests that you soften them by wrapping a slice of soft bread loosely in a paper towel and placing it in an airtight container with the cookies. Within 24 hours, you’ll have soft cookies, hard bread.
The other alternative is to repurpose your cookies. Chowhounds suggest breaking them in pieces and using them as mix-ins for ice cream or in place of ladyfingers or cake in a trifle; or folding them into lightly sweetened whipped cream. Chill overnight to make a kind of cookie mousse. Or crush them and use them to make a crumb crust for a pie or cheesecake.