Preheat your oven to 375 degrees F. Line a baking sheet with parchment paper. Set aside.
In the bowl of an electric mixer, fitted with the paddle attachment, combine the butter, peanut butter, brown sugar, milk and vanilla. Beat on medium speed until well blended, about one minute.
Add the egg and beat until just combined.
Add the flour, baking soda and salt and mix on low speed until just combined.
Stir in the peanut butter chips.
Using a cookie scoop (mine is about 2 tablespoons), drop cookie dough on lined baking sheet about 2 inches apart. Do not flatten these cookies like most peanut butter cookies call for.
Bake for 8 to 9 minutes, or until slightly golden brown on top. Do not over bake. In fact, I like these underdone just a little. Let the cookies cool for about 10 minutes before eating.
Makes about 14 large cookies.