1. Chocolate filling: Combine the gelatin, 1/2 cup of the granulated sugar, salt, water, and chocolate in a medium saucepan. Cook over medium heat, stirring constantly until the chocolate is melted. Pour about 1/2 of the mixture into the egg yolks.  Whisk vigorously.  Pour the egg /chocolate mixture back into the pan.  Cook over medium heat, stirring constantly, just until the mixture comes to a boil.
2. Immediately remove the pan from the heat. Place the pan in cold water and cool it until it slightly mounds on the back of a spoon.  Remove the pan from the water and mix in the vanilla. Set aside.
3. Whipped egg whites: Add egg whites and cream of tartar to a large mixing bowl of an electric mixer. Using the whisk attachment or metal beaters, beat the egg whites until a soft peak forms. Continue beating while gradually adding the remaining 1/2 cup of granulated sugar until egg whites form stiff peaks.
4. Gently fold the egg whites into the chocolate mixture until combined.
5. Gently fold in the whipped cream.
6. Transfer the filling to the pre-baked pie crust.  Refrigerate for at least 2 hours or overnight. Top with the freshly whipped cream topping and chocolate shavings.

 Topping

1. Add the whipping cream and powdered sugar to a mixing bowl.  If using a stand mixer, place a towel over the top.  Beat on high for about 30 seconds until the whipping begins to slightly thicken.  Add the vanilla and beat until medium/stiff peaks form.
2. Spread the topping over the pie.  Sprinkle with chocolate shavings if desired, and serve.
3. Refrigerate leftovers for up to 3 days.