I've read hundreds of posts on suggestions to solve the flat crispy cookie problem. I know it's only a problem if you don't like flat crispy cookies, half the population like flat, the other half likes thick and chewy. Often the flat cookie populace strives for thick and chewy and vice versa.
I've tried everything, chill the dough, froze the dough, melt the butter, not melt the butter, change white/brown sugar combination, Alton Brown's recipe, 5 different other chocolate chip cookie recipes, added up to 3/4 cup more flour, used dark pans, light aluminum pans, preheated the oven, calibrated the oven with two different thermometers, tap the pan after I take them out of the oven.
The issue is I don't really want to change the tollhouse recipe as my good friend, and it seems many others, can achieve thick chewy chickens with the same recipe. I 've even checked elevation differences between our cities to see if elevations make a difference.
Finally, I conducted a control study where I invited my friend to come over to my house to bake them. She brought all her own ingredients, utensils, and battered aluminum baking sheet, and....redemption! Her cookies made at my house in my oven came out flat!!!
I've narrowed it down to my oven (but I don't want to discourage any other ideas). My question to all you Bakers, Chemist, Physicist (yes I think it's become more of a scientific questions) rather than one of technique or ingredients, is could it be the heat intensity on my Thermodor professional oven even though it calibrates correctly at 375 and correctly pre-heated. Could it be that the intensity, humidity of the professional oven could be melting the butter too quickly or differently creating the air bubbles I see when I take the cookies out of the oven, where all the air swooshes out resulting in flat crispy cookies???