Preheat oven to 350 degrees. Line the bottom of a 9 x 3 inch cake pan with parchment paper; or generously grease and flour the bottom of the pan.
Sift together 1 cup cake flour, 1/2 tsp. baking powder and 1/4 tsp. salt. Set aside.
Cream 2 sticks of butter and 1/2 of the sugar until light and airy; about 2 minutes. Separate the eggs. Add 8 egg yolks, one at a time, lightly beating after each addition. Add 2 tsp. vanilla. Mix until well combined.
Mix in the sifted dry ingredients. Do not over-mix. Fold in 3/4 cup melted semi-sweet chocolate into the batter.
Whip 8 egg whites to soft peaks. Slowly add the remaining 1/2 cup sugar and whip to full peak. Fold the egg whites into the cake batter in thirds, mixing until there are no streaks of egg whites visible.
Pour the batter into the prepared cake pan; spread to an even level and bake until the middle of the cake springs back when pressed or a toothpick inserted into the middle of the cake comes out clean, which will be about 45 to 50.
Cool for 10 minutes in the pan; then turn out onto a rack and allow to cool completely. Once cooled, using a serrated knife, cut off the top of the cake so it is flat and level. Split the cake horizontally into 2 layers. Make the Apricot mixture.