1. Stir together butter and sugar in small bowl. Add graham cracker crumbs; mix well. Spread mixture firmly onto bottom of 8-inch square pan. Refrigerate 1 to 2 hours or until firm.
2. Meanwhile, heat milk to boiling in small saucepan; remove from heat. Immediately add chocolate bar pieces and small chocolate chips; stir until chocolate melts and mixture is smooth. Pour into medium bowl; cool to room temperature.
3. Beat whipping cream in small bowl on high speed of mixer until stiff; fold gently into chocolate mixture. Pour onto prepared crust; freeze several hours or until firm. Cut into squares. Just before serving, garnish with whipped cream and strawberries. 6 to 8 servings.