Cookie Biscuits: What happened? My wife made some chocolate chip cookies tonight using the same recipe she has for years; it's the one on the back of the Tollhouse Chocolate Chips bag. The only modification she makes to the recipe is that she uses half the butter, which ends up being only a half cup instead of a whole. Usually the cookies turn out round, flat, and about 1 cm high, but tonight we discovered a surprise. These are around an inch high and weren't completely cooked through the center as seen below.



Both of us being engineers, we are curious as to why this happened. We used the following steps and ingredients when making them:

Ingredients


2.25 Cups of Pillsbury all purpose flour
1 tsp Arm &amp; Hammer baking soda
1 tsp Morten salt
1 stick softened Fleichmanns original butter (normally uses Land-O-Lakes) (113g pure butter)
3/4 cup white sugar 
3/4 cup brown sugar
1 tsp vanilla
2 large eggs
2 cups Tollhouse Semi-sweet chocolate chips


Preparation steps


Preheated the oven to 375°F (190°C)
Whisked together flour, baking soda, and salt in a small bowl
Beat butter, white sugar, brown sugar, and vanilla with mixer until creamy.
Added eggs 1 at a time, beating well after each addition.
Gradually beat in the flour mixture
Stirred in the chocolate chips
Dropped dough balls in place on a cookie sheet. 
Cook for 9-11 minutes


The above steps are exactly what my wife did when we made these cookies. We noticed that the dough looked incredibly dense, sticky, and was very hard to mix after it was all combined. We used a mixer instead of hand mixing the dough like she has in the past, but I find it hard to believe that this would be the culprit (someone may very well prove the cooking n00b wrong though).

FWIW, please don't critique the recipe ;), as we really only want to know why they came out as biscuits when my wife has used this recipe exactly and successfully in the past. She has followed the same routine every time she has made them except for the use of a mixer and different brands of ingredients.
This looks to me like the symptoms of too much flour - probably way too much.

Measuring baking ingredients by volume instead of weight is always a crapshoot, although it shouldn't be that far off - my guess is that either the flour was heavily compacted, or perhaps the baker's mind wandered off and she accidentally added an extra cup.

Overmixing (i.e. by using an electric mixer) is a common problem with cookies but the symptom of that is a hard and gritty cookie that doesn't rise - not one that rises too much and has unbaked flour in the center.  As far as I know, that can only happen with a huge amount of flour.  Obviously, too much flour would also result in a much denser dough.

What you ended up with seems to be more like a quickbread - almost a scone - and there is indeed not an awful lot of difference between the two aside from the ratios and the creaming of butter.

Excess flour probably wouldn't result in a stickier dough, but stickiness is more due to temperature than anything else.  If you're finding the dough too sticky to mold then make sure it's thoroughly chilled - that will make it easier to work with.