Preheat oven to 350 degrees. Line baking sheets with parchment paper.
Combine brown sugar, white sugar, and butter. Beat until creamy. Add peanut butter, milk, egg, and vanilla. Mix until well blended.
Add baking soda, salt, and flour to the creamed mixture at low speed.
Use a 3 Tbsp. sized cookie scoop to scoop cookie dough onto the baking sheet. Flatten slightly in a crisscross pattern with a fork (if the dough sticks to the fork you can dip the fork in water first).Note: I bake 4 cookies, spaced out, per sheet for jumbo cookies.
Bake one baking sheet at a time for 12-13 minutes or until set and just beginning to brown. Do not over-bake.
Cool for 2 minutes on a baking sheet. Remove cookies to the cooling rack to cool completely.
Video
Notes
Wrap cooled cookies individually in plastic to keep them fresh. Cookies will stay soft for days. I bake with light-colored metal baking sheets. If you bake on dark metal you may need to adjust the baking time so that the bottoms of the cookies don't get too dark.