You will need:
In a medium bowl, cream together peanut butter and butter. Gradually blend in the brown sugar, white sugar, eggs, and vanilla; mix until fluffy. Combine flour, baking powder, and salt; stir into the peanut butter mixture until well blended.
Bake for 40-45 minutes in preheated oven, or until the top springs back when touched. Cool.
To make the icing, blend all icing ingredients together until light and creamy. Spread on top of the cool slice and cut into 16 squares.
I hope you enjoy this slice as much as I do!
Linking up with Real Family Fun and Kitchen Fun and Crafty Friday.