Using a hand mixer or a stand mixer fitted with a paddle attachment, cream your butter, sugars & vanilla together until light and fluffy. About 2-3 minutes. Add in the peanut butter and mix to combine. Next add in the egg.
Add in your dry ingredients and mix on low until there are not pockets of flour left. Using a spatula stir in your mix-ins. Reserve some for topping. Scoop the cookies onto a parchment lined sheet pan leaving space in between for spreading. Top with additional mix-in's. Bake for 10-12 minutes. Enjoy warm!