Preheat oven to 325°F. Grease and flour an 8 ½ by 4 ½ inch loaf pan. Alternately, use a 9x5 inch loaf pan. I used an 8x4 inch pan and it was a bit too small.
Whisk together the flour, baking powder, and salt and set aside.
Beat peanut butter and butter with electric mixer at medium speed, about 2 minutes or until creamy. Gradually add sugar, beating 5 to 7 minutes. Add eggs, 1 at a time, beating just until yellow disappears. Gradually add flour mixture, stirring just until mixed. Stir in vanilla. Pour batter into prepared pan.
Bake 1 hour and 20 minutes to 1 hour and 25 minutes or until long wooden pick inserted in center comes out clean. Note: This really does take a while to bake, so just keep testing it until it is done and lay foil over it if it starts browning too fast.
Cool in pan on wire rack 10 to 15 minutes; remove from pan, and cool completely on wire rack.
For the topping, combine ⅓ cup of miniature chocolate chips (or 2 oz of your favorite semisweet chocolate) with a teaspoon of coconut oil or shortening. Melt in the microwave using 50% power and stirring every 30 to 40 seconds. Drizzle over cooled cake, then sprinkle cut mini peanut butter cups over the top.