If using whole almonds, toast in a 375 degree oven for 5 minutes. Remove from oven and let cool. Pulse in a food processor into fine pieces. Set aside.
Heat a double boiler over simmering water. Add chocolate and butter and stir until melted. Turn off heat. (You can also do this with a large bowl over a pan of simmering water or in the microwave in 15 second intervals.)
Separate the egg whites from the yolks. Place whites in one mixing bowl and the yolks in another. Add the sugar to the egg yolks. Beat on high with an electric mixer until mixture is white and frothy, around 3 minutes. Stir in the melted chocolate, salt and ground almonds.
Beat the egg whites on high speed for about 5 minutes or until stiff peaks form. Using a spatula, gently fold the egg whites into the yolk-chocolate mixture until fully incorporated. Grease an 8 or 10 inch cake pan and pour in the batter.
Bake at 350 degrees for 45 minutes. Serve with whipped cream and powdered sugar.