3/4 c. sugar 
2 tbsp. cornstarch 
2 c. milk 
2 (1 oz.) squares unsweetened chocolate 
3 eggs, separated 
2 tbsp. margarine or butter 
1 tbsp. grated orange peel 
1 9 inch baked pie shell 
1/2 tsp. cream of tartar 
6 tbsp. sugar

Mix sugar and cornstarch in medium bowl. Stir in milk. Add chocolate squares. Microwave at High (100%) until smooth and thick, 6 to 8 minutes, stirring after 3 minutes. Stir a small amount of chocolate mixture into egg yolks; return to hot chocolate mixture, blending well. Microwave at Medium-High (70%) 3 minutes, stirring once. Stir in margarine and orange peel until margarine is melted. Pour into pie shell. Set aside. Preheat oven to 425 degrees. Beat egg whites and cream of tartar until foamy. Beat in sugar, 1 tablespoon at a time; continue beating until stiff and glossy. Spoon meringue onto chocolate filling; spread over filling, carefully sealing meringue to edge of crust. Bake 8 to 10 minutes, or until meringue is brown. Makes 9" pie.
 

Source: http://www.nancys-kitchen.com