Baking cookies: Why does the order of ingredients matter?

On the back of the Nestle chocolate chips package is the recipe for their Toll House chocolate chip cookies. The recipe calls for the butter, sugars, and vanilla to be mixed together and beaten, then two eggs added and further beaten. Then the flour (plus baking soda and salt) is added and the mixture is beaten. This is the way I’ve always done it.

Recently though, a friend of mine, who doesn’t do much baking, wanted to make the cookies. What she did was to just put all the ingredients into a bowl at once and then beat it (no double-entendres here, ok?).

Her cookies came out noticably different (and not as good, if I may say so) than mine usually do. Not only was the texture more like bread, but they definitely tasted different (more “doughy”, is the best I can describe it).

So my question is: Why does it matter? The stuff gets all mixed together either way, and then the process of baking should be the same. So why does beating the butter/sugar mixture first and then adding the flour make a difference in taste vs. just mixing it all together at the same time?

What you make when you throw in the flour too soon isn’t cookie dough – it’s bread dough (or possibly batter). The flour is hydrated and beaten to hell, forming lots of gluten. Gluten is a fine thing in bread, which is supposed to be cohesive and fine-grained, but it’s a rotten thing in a cookie, which is supposed to be crumbly.

Plus, if you put everything in at once, you won’t be able to break the butter down so that it’s evenly distributed throughout the mixture. Eggs would probably have the same problem.

I don’t know why, but this thread reminds me of an old Rita Rudner joke.

There is a lot of chemistry involved in cooking. And it can start in the mixing of substances, not just when you heat them. Certain ingredients must chemically bond with some ingredients but not so much with others.

Let’s not forget the leavener, in this case baking soda (it’s also baking powder, or cream of tartar in some instances). The later the leavener hits moisture, the later it begins to work, and therefore the cookies will rise higher in the oven.

The sugar, butter and eggs are supposed to form an emulsion, sort of like that found in vinegar and oil salad dressing. An emulsion is a relatively stable and intimate mixture of all it’s components; in this case, sugar, butter, and egg. The sugar in the mixture doesn’t so much dissolve in the butter and egg, rather it becomes almost a molecular scale suspension in a semiliquid. In other words, the butter and eggs melt those grainy sugar crystals, and prevent the sugar molecules from reforming new crystals. This gives a nice plastic (AKA chewy) texture to the finished cookie. You can sometimes get away with adding the egg to the butter before the sugar’s completely lost it’s crystal form, but if you add the flour too soon, it will suck up all the moisture and prevent the sugar crystals from breaking up. Plus, as Nametag mentioned, mixing wet flour too enthusiastically activates the gluten, which further degrades your cookie’s consistency.

Thanks to all who have responded. The answers have been very interesting and enlightening. Now I can tell my friend there are good scientific/chemical reasons for following the directions.

Good rule of thumb is to mix all “wet” ingredients first then add all the "dry"ones.

I dont think you’ll see much difference if you beat the eggs first then add the butter or vice versa. I just like doing the eggs first to have as a base to mix all the other indgredients better. BTW, be sure to use room temperature butter. It mixes better.