Our kids really like Costco muffins, but I find that we have a hard time using them up before they go bad. When we buy them, I immediately cut them in half, put them in a Ziploc bag, and freeze them. They are easy to defrost either ahead of time in the refrigerator or more quickly in the microwave. Be sure to use a low power, so that you don't dry them out.
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Muffins hold up in the freezer pretty well, however it is no more possible to restore that crispy right-out-of-the-oven top after freezing, than it would be if you stored them at room temperature.
