In order to freshen up ridiculously stale croissants, we recommend you first microwave your croissant, and then pop it into the oven. To do this, microwave your croissant for only a few seconds before placing your croissant into an oven preheated at 300 degrees for another 5-6 minutes. Microwaving first will reintroduce moisture into the croissant before you transfer it to the oven to reconstitute the original texture of the croissant. Remember, a stale croissant may never be as good as it was fresh, but microwaving certainly helps with the stale croissant taste and texture. There are also several recipes you can make with stale croissants, all of which taste delicious!