Preheat oven to 350 degrees F. Lightly grease a 9-inch square baking pan. For easier removal, line bottom of pan with parchment paper and lightly grease parchment paper.

Whisk together flour, baking powder, baking soda, and salt in a small bowl.

Beat eggs for 3 minutes in a large bowl using an electric mixer at high speed, or until thick and fluffy.

Add brown sugar to eggs and beat to combine until smooth.

Add peanut butter, melted butter, and vanilla to egg mixture. Beat until combined.

Add flour mixture and mix until just combined.

Place the chocolate and peanut butter chips in a bowl and toss to mix together.

Stir half of the chips into the batter.

Spread batter evenly in prepared pan.

Sprinkle top with remaining half of the chips.

Bake for 25 to 30 minutes or until lightly browned.

Cool completely in pan on a wire rack.

Cut into bars or squares.