Peanut butter, oatmeal, and chocolate chunks are a killer trio in these SUPER soft and chewy oatmeal chocolate chunk cookie cups! You won't be able to stop at only one.
Preheat oven to 350F. Grease two muffin tins and set aside.
Place butter and sugar in the bowl of a large stand mixer, fitted with a paddle attachment. Mix on medium speed until creamy, about 3 minutes. Add peanut butter, egg, and vanilla to bowl and mix until smooth.
Add oats, flour, baking soda, cinnamon, and salt to mixer and mix on medium speed until dough comes together. (dough will be slightly sticky) Gently stir in chocolate chunks.
Using a cookie scoop, scoop dough into 2-in balls and press into prepared muffin cups. Bake cookie cups at 350F 10-11 minutes or until edges are golden (cookies will appear underdone in the middle---this ok) Cool cookie cups 5 minutes in muffin tin, then transfer to a wire cooling rack. Enjoy cookies warm while the chocolate is gooey!