Preheat oven to 450 degrees F.
Grease a 9-inch pie pan.
To make the meringue, beat egg whites with a hand held electric mixer until soft peaks form. In a separate bowl, mix the sugar and cornstarch together, then add 2 tablespoons at a time to the egg whites, beating well between each addition. After the third addition, add the white vinegar. Before the last addition, add the vanilla extract. Place into the pie shell and press against sides to form a pie crust. Place in oven and turn off oven heat. Leave pie in oven at least 3 hours.
For filling, melt chocolate in a bowl over a double boiler. In another bowl, beat the yolks, sugar, salt, and water thoroughly. Stir mixture into melted chocolate. Cook mixture over double boiler stirring constantly until very thick. Cool mixture completely. Fold chocolate mixture into whipped cream. Pour into cooled shell and chill overnight.
Top with remaining whipped cream and garnish with chocolate shavings.