Preheat oven to 350 degrees F (175 degrees C). Grease an 8 inch square baking pan.
In large bowl, cream the shortening, brown sugar, vanilla and eggs. In a separate bowl, mix together the flour, walnuts, baking powder and salt. Slowly add to egg mixture, stirring until well blended. Spread dough evenly into the prepared pan.
Bake for 20 to 24 minutes, or until inserted toothpick comes out clean.