What in heaven's name happened to my cookies (photo)?

Too much flour when rolling them out, possibly. I use a pastry brush (old style, not the silicone ones) to brush off excess flour before I place them on the cookie sheet.

I dont use flour at all to roll mine out, I use silicone mats

I've had this happen to me, too, and I don't use flour. I roll on parchment or wax paper. I have NO idea why this happened, but if someone can tell us, it would be great!

This has happened to me as well. I always thought it was because the tops dried out while I was chilling them. If I stick them straight into the oven, I'm fairly sure this doesn't happen.

Was your butter too soft? This kind of thing is something I associate with recipes that call for melted butter as opposed to room temp butter. It's why brownies get that shiny, elephant skin surface. I also have two different recipes from Cooks Illustrated for chocolate chip cookies. They are pretty similar except one calls for creaming room temp butter and sugar and the other calls for melted butter. The first always comes out like normal chocolate chip cookies, the send comes out with that same elephant skin.

Room temp butter, in cooking terms for creaming, does not mean the temp of the room you're in. From The Joy of Cooking: "The temperature of the butter is very important in baking. When room temperature butter is used in your recipe this means your butter should be between 65 degrees F (18 degrees C) and 70 degrees F (21 degrees C). This temperature allows the maximum amount of air to be beaten into your batter. This creaming or beating of your butter or butter and sugar creates air bubbles that your leavener (baking powder or baking soda) will enlarge during baking. Most experts recommend 4 to 5 minutes of creaming the butter for maximum aeration."

At those temps, your butter will still be cool and firm, not squishy. This is just a guess. But if your butter was too soft, it may not have allowed enough air incorporation and taken on the qualities you get with melted butter.

Did you beat the dough a little longer than usual? I know brownies develop a shiny crust when you beat the batter more. Also what kind of sugar did you use? I'm browsing through my BakeWise book by Shirley Corriher because she usually has the answers to this sort of thing but not having much luck .

I've definitely had that happen before too- without having done anything notably different when preparing the recipe. I don't think the additional extract could have done it, I've added a TON of coconut flavor to some chocolate cookies and it had no effect whatsoever. Mystery!

Did you roll out your dough, leave for a few minutes (enough time for a skin to form on the dough) then finish rolling the dough a little thinner? I've had this happen with sugarpaste.

I've had this happen as well. I was thinking it may be from mixing scraps of dough after rolling with a piece from a new batch? I'd love to know the answer to this dilemmna too.