In a large saucepan over very low heat, melt chocolate. Add butter, stir until melted and remove from heat (the mixture should be body temperature, not too hot to touch with a finger).
In a large bowl, combine egg yolks, brown and white sugar, and stir until well mixed. Add the chocolate, and stir well until combined. In a small bowl, combine almonds, flour and cornmeal, stir until well mixed. Pour this into the chocolate and stir until combined.
In a large bowl with an electric mixer, beat the egg whites with cream of tartar until they form stiff peaks. Fold the egg whites into the chocolate in three batches.
Chef Dale Nichols warns that folding egg whites into chocolate takes a real knack and suggests using your hand as the paddle. To do this by hand, use your hand as a paddle and push your palm down to the center of the bowl, and slide up the side of the bowl and turn your hand over. Do not over-mix or you will knock the air out of the egg whites causing a much denser texture.
Bake in a buttered, floured 25 cm spring form pan for 5 minutes at 200ºC . Reduce heat to 180ºC and bake for another 20 to 30 minutes, or until cake tests done in the center.
Let cool completely before removing from pan.