With a mixer, cream together the peanut butter, butter, white sugar and brown sugar until blended.
Beat in the egg, milk, and vanilla.
Combine the flour, baking powder and salt in a separate bowl.
Add flour mixture to the peanut butter mixture and mix together. Stir in whatever mix of chocolate chips, peanut butter chips, mini Reese's pieces and regular Reese's Pieces you'd like! I used about 1/2 cup of each, reserving some of the Reese's Pieces for the top of the cookies.
Scoop tablespoonfuls of dough and roll into balls.
Place cookies 2 inches apart on parchment lined cookie sheets. Press additional Reese's Pieces onto each cookie dough ball.
Bake for 8-10 minutes at 375. Don’t overcook! These cookies are much better soft and just barely cooked all the way through. I baked the cookies scooped with the medium 1.5 TBSP scoop for 8 minutes and the 3 TBSP cookies for 10 minutes.