Preheat oven to 375°F. If you need to use two racks in your oven, adjust to divide the oven into thirds for even baking. Otherwise place rack in center of oven.
Cream together the peanut butter and shortening. Gradually add the brown sugar, beating until light. Add vanilla and eggs, one at a time, beating until fluffy.
In a separate bowl, sift together 2 cups sifted all-purpose flour, 2 teaspoons baking powder and salt. Add dry ingredients alternately with milk, beating after each addition. Fill paper muffin cups half full. Bake in preheated 375°F degrees for 15-20 minutes or until tester inserted in center comes out clean. Frost with fudge frosting.
Makes 2 dozen cupcakes.
Fudge frosting :