In the bowl of a food processor, combine the blanched almonds and bitter almonds or apricot kernels and grind to a fine powder, adding a little sugar if necessary to keep the nuts from sticking together. Set aside.
Melt 5 tablespoons butter over low heat in a small saucepan. Remove from heat and let it cool.
Grease a 9-inch cake pan with butter and set aside.
In a large bowl, sift together the flour, cornstarch and nutmeg.
Preheat the oven to 375 degrees F.
Separate the eggs and place the whites and yolks into separate bowls. Beat the yolks with a hand mixer and gradually add the ground almonds and the sugar, beating the mixture until it is light and fluffy. Gradually add in the flour mixture and cooled butter, beating vigorously between each addition.
In the other bowl, beat the egg whites until they are stiff and glossy, then fold them into the flour mixture. Pour the whole batter into the prepared cake pan and bake until the cake is firm and golden, about 40 minutes.
Let cool for 15 minutes, then turn out of the pan and let cool completely.
In a double boiler over very low heat, melt the chocolate, stirring constantly. Add 2 tablespoons water and stir until the chocolate is smooth and glossy.
Once the cake is cool, pour the melted chocolate on top and spread it with a spatula. Serve the cake at room temperature.