Add the flour mixture to the butter mixture in 2 to 3 parts, mixing until just combined after each addition.
The brown sugar is the real star of these cookies, and dark brown sugar has a richer, more molasses flavor than light brown sugar that is so good in these cookies. Should I use light brown sugar or dark brown sugar in oatmeal cookies? Why did I have so many oats? What was I trying to prove? Anyway, it turns out that brown sugar-not the oats-is really the star of the show (hence this recipe's title) and the result is a type of cookie that's as good at room temperature as it is warm straight out of the oven. So yesterday, in between the nine loads of laundry I knocked out, I set out to make chewy oatmeal cookies, partly because I discovered that I was in possession of six (!) large containers of oats.
Whether they're crispy or chewy, I don't care. But in recent days/weeks/months, I've really found myself drawn to cookies that are flat-out… well, flat. I never met a homemade cookie I didn't like, whether caky or crispy or chewy.