Frosted Peanut Butter Bars (Taste of Home)

1/2 cup peanut butter
1/3 cup shortening
1-1/2 cups packed brown sugar
2 eggs
1 tsp vanilla extract
1-1/2 cups all-purpose flour
1-1/2 teaspoons baking powder
1/2 teaspoon salt
1/4 cup milk

Frosting:
2/3 cup creamy peanut butter
1/2 cup butter flavor shortening
4 cups confectioners' sugar
1/3 to 1/2 cup milk

Topping: (I have never put this on before they are yummy without)
1/4 cup semisweet chocolate chips
1 teaspoon shortening

In a mixing bowl, cream peanut butter, shortening and brown sugar, beat in eggs and vanilla. combine the flour, baking powder and salt; gradually add to creamed mixture. Add milk; mix well. Transfer to a greased jelly roll pan. Bake at 350 for 16-20 minutes or until a toothpick inserted near the center comes out clean. Cool. For frosting, in a mixing bowl, cream peanut butter, shortening and confectioners' sugar. Gradually beat in enough milk to achieve spreading consistency. Frost bars. Melt chocolate chips and shortening; stir until smooth. Drizzle over frosting. Refrigerate.