Sift together 1/2 cup sugar and 1/2 cup flour, and add in 3/3 cup finely chopped almonds.
Beat together 5 egg whites, until they form soft mounds, and then add 1/4 tsp salt, 1/2 cup sugar and 1 tsp vanilla, beating until stiff and glossy peaks are formed.
Gently fold in the dry ingredients a few spoonfuls at a time. When combined, pour into two well-greased and floured 8-inch cake pans.
Bake at 350 degrees for 35-40 minutes.
When cool, frost top, sides and in between layers with Mocha Butter-Cream frosting, and sprinkle with slivered almonds.
For Mocha Butter-Cream frosting, beat together 5 egg yolks, 1/2 cup sugar, 3 Tbsp flour, and 1/4 tsp salt in a saucepan until light and fluffy.
Blend into egg mixture 1/2 cup cream and 1/2 cup strong coffee. Cook over medium heat, stirring constantly until thick. Remove from heat and add 1 Tbsp cocoa.
Blend in cocoa and cool to luke-warm. Add 1/2 softened and creamed butter, and 1 tsp vanilla.