In a large bowl, cream butter and brown sugar until light and fluffy. Beat in vanilla. Combine flour and baking powder; gradually add to creamed mixture and mix well. Stir in 1/3 cup pecans.
Shape tablespoonfuls of dough into acorn shapes, pinching bottoms to form a point. Place 2 in. apart on ungreased baking sheets. Bake at 350° for 8-10 minutes or until set. Remove to wire racks to cool.
In a microwave, melt chocolate chips and shortening; stir until smooth. Dip the top of each cookie in chocolate mixture, allowing excess to drip off. Immediately sprinkle remaining pecans over chocolate. Place on waxed paper; let stand until set.
Every editorial product is independently selected, though we may be compensated or receive an affiliate commission if you buy something through our links.