Preheat oven to 350 degrees F. Line a 9x9 inch baking pan with foil and grease.

With a FORK NOT A MIXER cream together butter and peanut butter. Gradually blend in the brown sugar, white sugar, eggs, and vanilla; mix until combined. Not fluffy. Combine flour, baking powder, and salt; stir into the peanut butter mixture until well blended

Fold in 2 cups chocolate chips and then spread into prepared pan.

Bake for 30 to 35 minutes in preheated oven, or until the top springs back when touched. Cool, and cut into 16 squares.