Preheat oven to 350F.
Butter and flour an 8 inch round pan. Set the chocolate and rum in a small pan and place off heat in a larger pan of almost simmering water; let melt while you proceed with the recipe.
Cream the butter and sugar together for several minutes until they form a pale yellow, fluffy mixture. Beat in the egg yolks until well blended.
Beat the egg whites and salt in a separate bowl until soft peaks are formed; sprinkle on the sugar and beat until stiff peaks are formed.
With a rubber spatula, blend the melted chocolate into the butter and sugar mixture. Then stir in the almonds (my almonds stuck together when a ground them so I added a little half of a cup of flour to get them loose and easy to incorporate) and the almond extract. Immediately stir in 1/4 of the beaten egg whites to lighten up the batter.
Delicately fold in a third of the remaining whites and when partially blended. Sift in one-third of the flour and continue folding. Alternate rapidly with more egg whites and more flour until all the egg whites and flour are incorporated.
Turn the batter into the prepared pan, pushing the batter up to its rim with a rubber spatula. This will prevent the middle from rising too much. Give the pan one light bang on the counter and bake in the middle of the oven for about 25 min.
The cake is done when it has puffed and 2 1/2 -3 inches around the circumference are set so that a toothpick plunged into the area comes out clean; the center should move slightly if the pan is shaken and a needle comes out oily.
Allow the cake to cool in the pan for 10 min. Run a knife around the edge of the pan and reverse cake on a rack. Allow it to cool for an hour or two; it must be thoroughly cooled if it is going to be iced.
Place the chocolate and rum in the small pan again and cover and set in the larger pan of almost simmering water. Remove pans from the heat and let the chocolate melt for 5 min. or so, until perfectly smooth.
Lift the chocolate pan out of the hot water and beat in the butter a tablespoon at a time with a wooden spoon. Then beat over ice and water until the chocolate mixture has cooled to spreading consistency. At once spread it over your cake with a spatula or knife.