4.5 oz AP flour (~1 cup minus 2 tbsp?)
1.5 oz oats (haldful and a half)
1/4 tsp baking soda
120 g butter**
1/4 packed brown sugar (plus a bit)
1/2 tsp salt
1/2 tsp vanilla
5 peanut butter cups, chopped (since cups come in packages of three, this is the obvious required number)
**About half of my butter was browned, half was not. I creamed the butter and the sugar, but you could probably brown all of the butter and just mix in the sugar. You can't properly cream browned butter anyway, since by heating it you've already broken the emulsion (this, by the way, is also why you shouldn't soften butter in the microwave). Using melted butter rather than creamed butter in cookies generally gives you a chewier cookie. It can also give you a flatter cookie, so I usually increase the ratio of dry ingredients to combat that a bit.
What to do:
Whisk together flour, oats, salt and baking soda and set aside.
In the bowl of an electric mixer, beat the butter until light and fluffy if you feel like bothering or, if you're lazy, just until soft. Beat in the sugars. I'm not always so lackadaisical about the importance of good creaming method, but in this case I wouldn't worry about it much (see above comment). If you've browned your butter instead, just mix in the sugars really well while the butter is still hot. Mix in the vanilla and then the egg until well combined. (If your butter is still hot, let it cool before mixing in your egg, lest you cook it. Although I HAVE wanted to try out these hard boiled egg cookies. Mind you, I never need to find a way to "use up" hard boiled eggs. Hard boiled eggs are delicious and so easy to eat on their own.)
Mix in your dry ingredients on a low speed, or by hand, until they are just incorporated. Fold in your chunks of peanut butter cup.
Chill while you pre-heat the oven to 375 F and prepare your baking sheet with parchment paper. Roll dough into ~2 tbsp balls. Bake for ten minutes, or until the edges are golden brown.
As ever, recall that leaving cookie dough in your fridge for a day or two makes for prettier, more delicious cookies. These photos are all of the ones I baked the next morning, rather than the couple I baked immediately.