1. In large bowl, beat butter, sugar, egg and vanilla until well blended. Stir together flour, cocoa, baking powder and salt; gradually add to butter mixture, beating until well blended. Divide dough in half; place each half on separate sheet of wax paper.

2. With hands, shape each half into log with squared sides, about 7 inches long and 2-1/4 inches wide. Wrap each log in wax paper or plastic wrap. Refrigerate until firm, at least 8 hours.

3. Heat oven to 325°F. Cut logs into 3/8-inch thick slices. Place onto ungreased cookie sheet. Bake 15 minutes or until set. Cool slightly; remove from cookie sheet to wire rack. Cool completely. Remove wrappers from chocolate pieces.

4. Prepare Quick Cookie Glaze; drizzle over top of cookies. Immediately place a chocolate piece on each cookie. About 3 dozen cookies.

Quick Cookie Glaze: In small bowl, stir together 3/4 cup powdered sugar, 3 to 4 teaspoons milk, 1/4 teaspoon vanilla extract and 3 or 4 drops green food color, if desired, until of drizzling consistency.