Preheat oven to 350˚F. Lightly grease 9 x 13-inch pan.

In a bowl mix together flour, baking powder and salt

In another bowl, beat sugars, butter and peanut butter until smooth. Beat in eggs, one at a time, until incorporated. Stir in vanilla. Blend in flour mixture. Spread evenly in prepared pan. Sprinkle pieces of peanut butter cups over batter and press down slightly. Bake in preheated oven for 20 to 25 minutes or until a tester inserted in the center of cake comes out clean. Place pan on a rack to cool slightly.

Chocolate Drizzle: In the top of a double boiler over hot (not boiling) water, melt chocolate chips with butter, stirring until smooth. Drizzle over top of warm cake. Cool completely, then cut into bars.