good-quality dark chocolate or milk chocolate curls or shavings for garnish (optional)
Preheat oven to 190°C.
In a food processor, pulse wafers into very fine crumbs. (You should have 1¼ cups.) In a medium bowl, melt 4 tablespoons butter; add crumbs and 1 tablespoon sugar. Stir until moistened. Firmly press mixture into bottom and up side of a 22cm pie plate.
Bake for 10 to 12 minutes or until set. Leave to cool on a wire rack.
In a heavy 2,8-litre saucepan, whisk cornflour, salt and 1 cup sugar. While whisking, gradually add milk. Cook on medium-high for 7 to 8 minutes or until boiling and thickened, whisking constantly. Remove from heat.
In a large bowl, whisk egg yolks until blended. Whisk in hot milk mixture in a steady stream. Return mixture to saucepan and cook on medium for 4 to 6 minutes or until mixture boils and thickens, stirring constantly. Remove from heat and add chocolate. Stir until melted, then stir in remaining 2 tablespoons butter until melted. Stir in rum, if using.
Pour mixture into cooled pie crust and spread evenly. Press sheet of cling wrap directly against surface. Refrigerate for at least 4 hours or overnight, or until cold and stiff.
When ready to serve, beat whipping cream until thickened. While beating, gradually add remaining 2 tablespoons sugar. Beat until soft peaks form. Dollop cream over pie. Garnish with chocolate curls, if desired.
EACH SERVING About 1 528 kJ, 5g protein, 39g carbohydrates, 22g total fat (13g saturated fat), 2g fibre, 113mg cholesterol, 185mg sodium.