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

In a large mixing bowl, cream the shortening, peanut butter and brown sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Add vanilla. Combine the flour, baking powder and salt; add to creamed mixture alternately with milk.
Fill paper-lined muffin cups with 1/4 cup of batter. Press a peanut butter cup into the center of each until top edge is even with batter. Bake at 350 degrees F for 22-24 minutes or until a toothpick inserted on an angle toward the center of the cupcakes comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.

Source: allrecipes.com