Line 8-inch square pan with foil, extending over edges to form handles for easier serving. Mix Crust Mix, butter and sugar thoroughly with fork in medium bowl until crumbs are well moistened. Press firmly onto bottom of prepared pan using measuring cup.
Beat milk and Filling Mix with electric mixer on low speed until blended. Beat on medium speed 3 minutes. (Filling will be thick.) Spread half of the filling over crust. Stir chocolate into remaining filling; spread over filling in pan. Sprinkle with pecans.
Freeze 4 hours or overnight. To serve, lift from pan to cutting board, using foil handles; remove foil. Let stand at room temperature 10 minutes for easier slicing. Store leftover bars in freezer.