Preheat oven to 350°. Line a cookie sheet with parchment paper, or spray with non stick spray.
Cream the butter and sugar together for 3 minutes. It will become light and fluffy. Scrape down the sides and mix in the peanut butter, eggs and vanilla until well incorporated.
Add the flour, baking powder and salt. (I usually toss it all in at once and mix slowly) Mix until just combined. Stir in the chocolate chips.
Press the dough into the bottom of a parchment paper lined cookie sheet. (21"x15") Bake at 350° for 10-12 minutes, or until the center is puffy and is no longer glossy. You'll want to pull them before they start to brown.
Once the cookies have cooled, combine the milk, butter and sugar in a sauce pan. Bring it to a rolling boil and boil for 45 seconds. Take off of the heat and stir in the vanilla, chocolate chips and peanut butter. Pour over the sheet of cookies immediately.
Let the frosting cool and dry completely before cutting. Cut, drool, eat and repeat!