NOTE: Even though the egg whites are heated for the meringue, the egg whites are not heated to a high enough temperature to remove the risk of salmonella. If salmonella is a concern, use pasteurized eggs in the shell.
Line a sheet pan with foil. Using a ⅓ cup ice cream scoop, place a scoop of ice cream on ½ of a graham cracker. Place graham cracker on the foil lined sheet pan. Repeat with remaining graham cracker halves for a total of 8 graham cracker halves and 8 scoops. Place ice cream topped graham crackers in the freezer.
Fill a saucepan with about 2 inches of water and bring to a simmer. In a heat proof bowl or the metal bowl of a stand mixer add the egg whites and the sugar and whisk to combine. Place the bowl over the saucepan of simmering water and whisk until the sugar dissolves and the mixture thickens and turns from pale yellow to white. Using a thermometer, continue to cook (and whisk!) until the mixture reaches 140 degrees.
Carefully remove the bowl from the saucepan and using a mixer with the whisk attachement, whip the egg white mixture until it is smooth and glossy and holds a stiff peak when the beater is removed. Beat in the cream of tartar and the vanilla.
Remove the ice cream scoops from the fridge and frost with the meringue. Return "frosted" ice cream to the freezer for 30 minutes. If freezing for longer, carefully cover with plastic wrap. To keep plastic wrap from touching the tops of the baked alaskas, use a toothpick inserted in several of the scoops to drape the plastic over!
To brown the meringues, pre heat your broiler with the rack in the upper middle of your oven. Remove plastic wrap and toothpicks from ice cream. Place the baked alaskas under the broiler for 1 - 2 minutes. WATCH carefully and remove as soon as the meringues have browned!
You can also do this with a creme brulee torch if you have one. Simply remove the baked alaskas as outlined above and use the torch to brown the meringues.