Good catch – those tips were added years after the original post. Original recipe uses both. I use margarine and butter in these – so they hold together like a cakey cookie but also stay super buttery. You can use all butter – but the cookies might spread a bit more when baking.

I have tried freezing the dough both after mixing and after rolling – but before baking. The dough does get a little dry this way. I found that rerolling it between my hands to soften the exterior prior to baking did help with the overall texture of the baked cookies. I have not tried freezing the cookies once baked. I am not a fan of the color bleed with the M&M’s when they start warming to room temperature. They tend to sweat and become unappealing. I’m definitely a freshly baked cookie person though. That said, these cookies will keep in an airtight container for several days and still be soft. But there’s nothing like them fresh.

Ours have never lasted longer than a couple of days, and I am personally not fond of previously frozen cookies. I typically like to make them as close to the event as possible.

In your case, with so many days still before Christmas, I would recommend wrapping each cookie individually in plastic wrap and then placing them in an airtight container until ready to serve. For best results – you can make the dough ahead of time (since you need to chill it before baking anyway) and then bake them just before you plan to serve them. I do recommend mixing in the M&Ms just before baking as the color will sometimes bleed in the cool air of the fridge or freezer.