In a large bowl, cream butter and sugar. Add eggs, one at a time, beating well after each addition. Beat in extract. Combine the flour, baking powder and salt; stir in peppermint candy. Gradually add to creamed mixture, beating until blended (dough will be stiff).
Divide dough in half. On an ungreased baking sheet, shape each portion into a 12x2-1/2-in. rectangle. Bake at 350° for 25-30 minutes or until golden brown. Carefully remove to wire racks; cool for 15 minutes. Transfer to a cutting board; cut diagonally with a sharp knife into 1/2-in. slices. Place cut side down on ungreased baking sheets. Bake for 12-15 minutes or until firm. Remove to wire racks to cool.
In a microwave-safe bowl, melt chocolate chips and shortening; stir until smooth. Dip one end of each biscotti into melted chocolate, allowing excess to drip off; sprinkle with candy. Place on waxed paper; let stand until set. Store in an airtight container.