Preheat oven to 325 degrees F (165 degrees C). Grease a 10 inch tube pan.
Separate the egg yolks from the whites and keep the egg whites cold.
Combine milk, 1 1/2 cups of the sugar, 1 cup of the butter and all of the chocolate and bring to a boil in the top half of a double boiler over medium heat. Let cool slightly and stir in the egg yolks, flour, and baking powder. Beat for about 2 minutes with an electric mixer on medium speed.
In a glass or metal bowl beat the egg whites until stiff. Gently fold the beaten egg whites into the chocolate mixture. Pour batter into a greased 10 inch tube pan.
Bake for 50 minutes at 325 degrees F (165 degrees C). Let cake cool in pan for 15 minutes then turn out on to a wire rack to finish cooling.
To Make Frosting: Melt 1 cup sugar in a heavy pan. Once melted and slightly amber colored add the finely chopped nuts. Pour into a buttered flat sheet pan to cool. Once cool and set crush to a powder using a food processor.
Cream 1/2 cup of the butter until light and fluffy, gradually mix in the nut powder and the confectioners' sugar beating until smooth and creamy. Spread frosting over top of cake and garnish with whole pecan halves.