Preheat the oven to 250 degrees F. Draw two 8-inch circles on a sheet of parchment paper and place it on a sheet pan, pencil side down.
In the bowl of an electric mixer fitted with the whisk attachment, beat the egg whites, cream of tartar, and salt on high speed for one minute, until frothy. With the mixer on high, slowly add the 2/3 cups sugar and 1 teaspoon of the vanilla and beat on high for 2 minutes, until it makes firm, glossy peaks.
Divide the meringue between the two circles and spread into two flat 8-inch disks with a rubber spatula. Bake the meringues for one hour, turn the heat off, and leave the meringues in the oven for 2 hours. Remove them from the oven and allow to cool completely to room temperature on the sheet pan.
With a large flat spatula, carefully transfer one disk, rounded side up, to a totally flat serving plate. (It's okay if the top cracks a little.) Spread the chocolate pecan filling evenly on top. Place the second meringue, rounded side up, on top.
Combine the heavy cream, the 2 tablespoons sugar, and the remaining 1 teaspoon of vanilla in the bowl of an electric mixer fitted with the whisk attachment and beat on high speed until it forms firm peaks. Spread the whipped cream on top of the torte. Decorate with the shaved chocolate and refrigerate for 2 hours or for up to a day and serve cold.
Chocolate Pecan Filling:
In the bowl of a food processor fitted with the steel blade, process the pecans until finely ground. Set aside.
In a medium bowl set over a pan of simmering water, whisk the eggs, sugar, and cornstarch together, making sure the bottom of the bowl doesn't touch the water. Whisk the mixture almost constantly, until it is 130 to 140 degrees and thickened like custard. Set aside to cool to room temperature, whisking occasionally.
Set another bowl over the pan of simmering water, making sure the bottom of the bowl doesn't touch the water. Put the chocolate and espresso in the bowl and heat just until the chocolate melts, stirring occasionally. Stir in the Kahlua and vanilla and set aside to cool to room temperature. Whisk the chocolate mixture into the egg mixture, then whisk in the butter, one tablespoon at a time, whisking until smooth. Stir in the pecans. The filling can sit at room temperature for up to 4 hours.
This recipe has been updated and may differ from what was originally published or broadcast.