For fudge sauce, in a small saucepan combine the 1 cup sugar, the evaporated milk, butter or margarine, and chocolate. Cook and stir over medium heat until bubbly. Reduce heat and boil gently for 4 to 5 minutes, stirring occasionally, until mixture is thickened and reduced to 1-1/2 cups. Remove from heat; stir in vanilla. If necessary, beat until smooth with wire whisk or rotary beater. Set aside to cool completely.
In a chilled bowl, stir 1 pint of the ice cream until softened. Spread into cooled pastry shell. Cover with half of the cooled fudge sauce. Freeze until nearly firm. Repeat with remaining ice cream and fudge sauce. Return to freezer while preparing meringue.
In a medium mixing bowl dissolve 3/4 cup sugar in the boiling water. Cool to room temperature. Add the meringue powder. Beat on low speed until combined; beat on high speed until stiff peaks form (tips stand straight). By hand, fold 3 tablespoons of the crushed candy into the meringue. Spread meringue over chocolate sauce layer, sealing to edge. Sprinkle top with remaining crushed candy. Freeze until firm (several hours or overnight). Bake in a 475 degree F oven for 3 to 4 minutes or just until meringue is lightly browned. Cover loosely and return to freezer for a few hours or overnight before serving. Makes 8 servings.