Mix and pat into 9-by-13 pan.
Bake at 350 degrees for 20 minutes.
Filling: Stir the sugar, cornstarch, and salt together in a double boiler.
Blend egg yolks and milk, and add to the sugar mixture.
Cook until thick.
Remove from heat, add vanilla and chocolate, and let cool.
Put into crust.
Spread top with whipped cream or Cool Whip and sprinkle with toasted coconut.