In a small mixing bowl, cream butter and sugar. Beat in egg and lemon juice. Combine the flour, drink mix, baking powder and salt; gradually add to creamed mixture and mix well.
On a lightly floured surface, roll out dough to 1/4-in. thickness. Cut with a floured 2-1/2- to 3-in. heart-shaped cookie cutter. Place 2 in. apart on ungreased baking sheets. Bake at 350° for 8-10 minutes or until set and edges begin to brown. Cool for 2 minutes before removing to wire racks to cool completely.
In a small microwave-safe bowl, melt chocolate chips and shortening; stir until smooth. Spread over cookies; let stand until set.
In a small mixing bowl, cream the butter, drink mix and salt. Gradually beat in confectioners' sugar. Add enough milk to achieve desired consistency. Decorate cookies. Yield: about 2 dozen.