Grease a 750 ml wide mouth mason jar with shortening. Arrange the racks of your oven to accommodate the height of the jar. Preheat oven to 350 F.
In a large bowl, whisk together all the ingredients for the cake base until the batter is smooth. The batter should be thin enough to pour.
Pour the batter into the prepared jar; it should fill the jar about ¾ full. Do not over fill it or it will overflow during when it bakes.
Bake for 40-45 minutes until a long toothpick comes out clean. Cool completely.
Once cooled, gently tap the bottom of the jar to release the cake. Slice the cake into 2 cm wide rounds. Place rounds on a tray.
Using an ice cream scoop size that has a diameter similar to that of the cake circles, place a scoop of ice cream on top of each slice of cake.
Place in freezer for at least 3 hours.
In a double boiler, whisk together the egg whites, sugar and cream of tartar. Keep whisking for 2-3 minutes until the egg reaches a temperature of 160 F.
Remove from heat and transfer to a bowl and beat with an electric mixer on high until stiff glossy peaks from.
Remove the cakes from the freezer and quickly spread a good amount of meringue over the cakes so that the ice cream is fully covered.
Using a kitchen torch, brown the meringue. You can also use an oven broiler, just make sure the cakes are at least 8 inches from the broiler. Broil for 2-3 minutes until browned, and serve immediately.
Try to use a jar with straight edges so that the cake can slide out. If you don’t have a large jar handy, you can also use several smaller mason jars.
You can prepare the cakes with ice cream in advance and just keep in the freezer until ready to serve.