Line bottom of a 9-in. square baking pan with parchment. In a small heavy saucepan, cook and stir butter, sugar and cocoa over medium-low heat until butter is melted. Remove from heat., In a small bowl, whisk a small amount of hot mixture into egg; return all to pan, whisking constantly. Cook 2-3 minutes or until mixture is just thick enough to coat a metal spoon and a thermometer reads at least 160°, stirring constantly. Remove from heat., Stir in cracker crumbs, coconut and pecans. Press into prepared pan. Refrigerate 30 minutes or until cold., For filling, in a large bowl, beat butter and custard powder until blended. Beat in confectioners' sugar and half-and-half until smooth. Spread over crust. Refrigerate, covered, 1 hour or until firm., For topping, fill a small resealable bag with melted white chocolate; set aside, keeping warm. In a microwave, melt chocolate chips and shortening; stir until smooth. Spread chocolate mixture evenly over filling. , Cut a small corner in bag with white chocolate. Working quickly, pipe parallel lines over chocolate layer, spacing lines 1/4 to 1/2 in. apart. Working at right angles to the white chocolate lines, pull a toothpick back and forth across the pan, cutting through the piped lines to create a feather design. , Refrigerate 10 minutes or until topping is just set (do not allow the chocolate to harden completely). Cut into bars. Store in an airtight container in the refrigerator.