Cake in a Jar

Preheat the oven to 180°C (approximately 350°F)

Prepare the jars: grease with soft butter and sprinkle with ground almonds.

For the batter: chop the chocolate coarsely, and melt it with the espresso in a double boiler. Mix the butter with 150g (approximately 5 ounces) sugar and cinnamon until smooth. Add the egg yolks and continue stirring until the mixture is light and airy. Add the remaining sugar and continue beating until the mixture is smooth and glossy. Pour the butter mixture into the chocolate, then mix in the almonds and cornstarch alternating with the egg whites, folding gently until smooth. Fill the greased and floured jars approixmately 3/4 with batter, and bake in preheated oven for about 30 minutes. Test with a toothpick, then seal the jars. Place the sealed jars in a boiling water bath and bake again about 30 minutes at 100°C (approximately 225°F) in the oven. Allow to cool and store in a cool, dark place before serving.