Place the piece of cake on top of the ice cream, press down lightly, and if desired, brush the cake with 1 tablespoon of white creme do cocoa. Place the pan in the freezer for 1 hour. {You want the ice cream to be as hard as possible.
After an hour, combine the sugar, corn syrup, and water in a 2-quart saucepan and place over high heat. Stir just until the sugar dissolves, about 5 minutes. Clip on a candy thermometer and bring the mixture to 240 degrees F. {I was winging this part. I don’t have a candy thermometer. While the syrup is cooking, place the egg whites, salt and vanilla into the bowl of a stand mixer and, using the whisk attachment, whisk the eggs on high speed until they reach medium peaks, 4 to 5 minutes. When the syrup reaches 240 degrees F, remove from the heat and with the stand mixer on low, slowly pour the syrup in a thin steady stream into the egg white mixture, being careful not to come in contact with the whisk. Once all the syrup has been added, increase the mixer speed to high and whisk until stiff peaks are formed and the mixture has cooled, 8 to 10 minutes Remove the loaf pan from the freeze. {You want the ice cream to be rock hard} Turn the ice cream upside down onto a heatproof serving platter, and remove the plastic wrap. completely cover the ice cream and cake with a 1″ layer of meringue all around, sealing in the meringue to the pan around the bottom edge. {If you think you have enough meringue, you don’t. You need a really, really thick layer to keep the ice cream from melting when you torch the meringue.}