Preheat oven to 350 degrees. Combine the peanut butter, butter, and sugars. Beat until creamy. Add eggs and flavorings and blend well. Combine flour, baking powder, and salt. Stir into peanut butter mixture. Spread into a greased 9x13 pan. Sprinkle chips on top. Place in oven for 5 minutes only. Remove from oven and with a knife cut through the batter to marbelize. Return to oven and bake for 30 minutes longer.