In a large bowl, mix together the peanut butter, shortening and egg until well blended. Stir in the sweetened condensed milk and vanilla. Combine the flour and baking powder; stir into the peanut butter mixture to form a dough. Finally, stir in the chopped peanuts. Shape dough into 1 inch balls and place them 2 inches apart onto ungreased cookie sheets. Flatten balls using the tines of a fork.
Bake for 8 to 10 minutes in the preheated oven, until the edges are lightly browned. Remove from cookie sheets to cool on wire racks.