Here's the link to the recipe:
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Hi thepuffin. It will be fine in a 9 x 13 pan. The cookie will be just a teeny bit thicker. Tricky part is going to be the baking time, so start checking for doneness around 30 minutes or so. They sound amazing!!
hardlikearmour is a trusted home cook.
The area of an 8x8 is 64, so doubled is 128. The area of a 9x13 is 117 - which is close enough. Like mrslarkin said, it will be slightly thicker, and I'd expect them to take 5 to 10 minutes longer than the directions call for.
Go for it. Agree with above. :)
Same here, I often double a coffee cake recipe that is intended for an 8x8 pan to a 9x13 and it comes out just fine.
Just to say thanks for all the very helpful answers, as I am making this dish for a group!