Preheat the oven to 350°F. Line two cookie sheets with parchment paper or silicone baking sheets.

In a medium bowl, combine flour, salt, and baking soda; whisk together. Set aside.

In the bowl of a stand mixer, combine the butter, peanut butter, light brown sugar, and granulated sugar. Mix on medium speed for 2 minutes, until light and fluffy, scraping the sides of the mixing bowl as needed.

Add the egg, vanilla extract, and milk. Mix until fully incorporated. Decrease the mixer speed to slow, and gradually add the flour mixture. Beat until just combined. Add the peanut butter chips and chocolate chips, and pulse the mixer several times until evenly distributed.

Using a #16 ice cream scoop (or a ¼ cup measuring cup), scoop the dough into balls and place them on the prepared cookie sheets. Be careful not to overcrowd the dough, leaving approximately 3” between each cookie.

Bake for 14 - 16 minutes, or until the edges are golden brown. (Optional: 11 minutes into baking, gently press a few additional chocolate chips into the top of each cookie.

When done baking, rap the cookie sheet against the counter several times to help better distribute the melty chocolate chips.

Allow to cool for 5 minutes before moving to a cooling rack. Cool fully before serving.