1. Place egg whites in a small bowl and let stand at room temperature for 30 minutes. Add cream of tartar and beat on medium speed until soft peaks form. Gradually beat in sugar, 1 tablespoon at a time, on high until soft glossy peaks form and sugar is dissolved. Spread evenly into a well-greased 9-in. pie pan. Bake at 275° for 50 minutes. Cool on a wire rack.
2. For filling, melt chocolate in a small heavy saucepan or microwave; sir until smooth. Stir in coffee and vanilla. Cool to room temperature.
3. In a chilled small bowl, beat cream until soft peaks form. Fold into chocolate mixture. Pour into the meringue shell. Sprinkle with nuts if desired. Refrigerate, for several hours before serving. Refrigerate leftovers. Yield: 6-8 servings.