Prepare Mocha Pastry Shell as directed; set aside. Place 1 square chocolate in top of a double boiler; bring water to a boil. Reduce heat to low; cook until chocolate melts. Let cool. Cream butter at medium speed of an electric mixer. Gradually add brown sugar, and beat at medium speed 2 to 3 minutes, scraping sides of bowl occasionally. Stir in melted chocolate and 2 teaspoons coffee powder. Add eggs, one at a time, beating 5 minutes after each addition. Pour filling into cooled pastry shell. Refrigerate at least 6 hours. About 1 or 2 hours before serving, combine whipping cream, powdered sugar, and 1-1/2 tablespoons coffee powder in a large, chilled mixing bowl. Whip cream until soft peaks form (do not overbeat). Spoon over chilled filling. one 9-inch pie. MOCHA PASTRY SHELL: Use a fork to combine crumbled piecrust stick and chocolate in a medium bowl. Stir in walnuts and sugar. Combine water and vanilla; sprinkle over pastry mixture. Mix with fork until mixture forms a ball. Line a 9-inch pieplate with aluminum foil; place a circle of wax paper over foil in the bottom of pie plate. Press pastry mixture evenly into pieplate. Bake at 375 degrees for 15 minutes; cool completely. Invert crust on an 8-1/2-inch pieplate; remove foil and wax shell. ----