Preheat oven to 350 degrees. Grease and flour a 10x15 baking dish.
In stand mixer, combine eggs, sugar and vanilla. Beat on high speed until light.
Mix together flour and baking powder and add to the stand mixer in increments on low speed.
In a microwave safe bowl, heat milk and 2 tablespoons butter about 2 minutes, until it begins to bubble. Fold milk butter mixture into cake batter until combined.
Pour batter into prepared baking dish. Bake in oven for 20-25 minutes, or until an inserted toothpick comes out clean.
Allow cake to cool to room temperature before spreading peanut butter evenly over entire top of the cake.
Refrigerate to set, about 1 hour.
Add the chocolate chips and shortening to a microwave safe bowl and microwave for 30 seconds, then stir and microwave for additional 15 seconds until fully melted.
Spread melted chocolate evenly over peanut butter layer. Allow chocolate to harden and set before cutting and serving. Cut into 42 - 2 inch squares
