In a small mixing bowl, cream butter and confectioners' sugar until light and fluffy. Beat in lemon peel. Combine flour and cornstarch; gradually add to creamed mixture and mix well. Cover and refrigerate for 1 hour or until easy to handle.
Shape into a 1 3/4 inches diameter roll; roll into non-pareils. Wrap in plastic wrap. Refrigerate for 2-3 hours or until firm.
Unwrap and cut into 1/4 inch slices. Place 1 inch apart on ungreased baking sheets. Bake at 375 for 9-11 minutes or until set and edges are lightly browned. Cool for 1 minute before removing to wire racks to cool completely.
In a small bowl, combine icing ingredients. Spread over cookies.