You can bake oatmeal cookies in a mini muffin pan to stop them from spreading in the oven, yielding a thicker cookie with a more even bake. These oatmeal cookies are soft in the middle when they come out of the oven!
Grease two 24-mini muffin pans. Set aside. Also line a large rimmed baking sheet with parchment paper and set it aside.
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and the sugar for 2 minutes. Scrape down the sides of the bowl.
Add the egg, and beat again until incorporated.
Add the vanilla, and beat again. Scrape down the bowl.
In a separate bowl, whisk together the flour, baking soda, salt, and oats.
Add the flour mixture to the mixer bowl, and mix on low til the dough comes together.
Scoop the dough with a ¾ oz scoop (~20 g of dough per scoop) and place on the parchment lined sheet (I got exactly 24 scoops of about 20–22 grams). Refrigerate the dough for about 1 hour.
Preheat the oven at 350 °F (175 °C). When the dough is completely chilled, divide each scoop into two using a knife and place each half in a well of greased muffin pan.
Bake for about 10 minutes or until the edges are just beginning to turn golden brown. Let the cookies firm up for a minute or two before, unmolding with the help of a mini offset spatula.
Notes
I used
quick oats, which are finer than rolled oats (also called large flake oats). The two types of oats are not interchangeable. Use quick oats!