Preheat oven to 325 degrees. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, peanut butter, and sugars, until smooth and fluffy. Add the egg and vanilla extract and beat to combine. In a separate bowl, mix the flour, baking soda, and salt. Slowly add the flour mixture into the butter/sugar mixture mixing well after each addition. Finally, stir in the chocolate chips.