PREHEAT oven to 375ºF.
Topping Mixture:
MIX the 1/2 cup of brown sugar, 1/2 cup flour, the 1/4 cup of peanut butter and the melted butter or margarine till crumbly; set aside.
Cake Mixture:
CREAM the 1/2 cup peanut butter and the Shortening together well. Slowly beat in 1 cup brown sugar.
ADD eggs, one at a time, beating till fluffy.
STIR till well blended the 2 cups flour, baking powder, salt, and soda.
ADD alternately with milk to creamed mixture, beating after every addition.
SPREAD batter in a greased 13 x 9 x 2-inch baking pan.
TOP with topping mixture.
BAKE in 375ºF oven for 30 to 35 minutes.