Preheat oven to 350°. Prepare cookie sheets by lining with parchment paper, silpat liner or cooking spray.
In a large bowl with a handheld mixer, or the bowl of a stand mixer, add the butter, granulated sugar, brown sugar, and peanut butter. Mix together until it is well combined and light in color. Add in eggs and vanilla extract. Blend together.
Add flour and baking soda into the bowl and mix to combine together. I found this easiest to do with a wooden spoon (it will take a few minutes because the dough is thicker). When the flour is almost incorporated, add in the peanut butter chips and crushed Butterfingers. Mix just until combined.
Roll cookie dough into a ball, about 1-2 tablespoons of dough (size of a golf ball), or use a medium cookie scoop to scoop the dough and then roll into a ball. Place 12 cookies per cookie sheet.
Bake for 9-11 minutes.Cookies do not spread much while baking. When the cookies are done they will be puffy and thick looking. You don't want to overbake peanut butter cookies because they will be dry if overcooked. Remember that the cookies will cook slightly more while cooling. I have never baked these cookies longer than 9 minutes.
Let cookies cool on cookie sheet for a few minutes and then remove to a wire rack. You can leave cookies thick & puffy, or press a few additional peanut butter chips/Butterfinger chunks on tops of the cookies to gently press the cookie down.
Peanut Butter : Creamy works best in these cookies. I would not recommend using all-natural peanut butter. It's thicker which tends to make baked goods (like cookies) be really dry. Butter : I always use salted butter because it adds more flavor to baked goods. If you are used to baking with unsalted butter then that can easily be used instead. You may have to add additional salt (optional) if using unsalted butter.