i've actually never used aluminum foil. usually i just use wax paper if i don't have parchment, or just the plain old cookie sheet. i'm sure they'll turn out fine though.
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I never bake cookies on parchment paper. I just put them straight on the pan. I think the aluminum will make them bake faster (maybe make the bottom burn)
Ok thanks ladies. For my next batch I'll just remove the aluminum foil and put them directly on the cookie sheet. I've always used parchment paper, but I forgot it at the store. Thanks!
Re: What happens if cookies are not baked on parchment paper
I think they can get too hot. I would just check them a little more frequently.