Sift dry ingredients together.
Cream butter and 3/4 cup sugar. Beat in egg yolks and orange rind. Blend orange juice with 3 tbsp rum, almond extract and vanilla. Add alternately with dry mixture to the creamed ingredients.
Beat egg whites until stiff; beat in remaining 1/4 cup sugar until whites hold stiff peaks. Fold into the batter.
Pour into two 8-inch or 9-inch round cake pans lined with waxed paper. Bake in moderate oven 350º F for 25 minutes or until done.
Cool 5 minutes then turn out to complete cooling on wire racks. Peel off paper when cakes are taken from pans. (Mom's note, she does not bother with the paper). When cold, split each layer crosswise to make four thin cake layers.
Whipped Cream Filling: soften 2 tsp gelatin in 2 tbsp cold water. Dissolve over hot water.
Put 2 cups whipping cream into chilled bowl. Beat until cream begins to thicken. Slowly add 1/2 cup icing sugar. Gradually blend in 1/3 cup light rum. Slowly pour in gelatin, beating until cream holds its shape. Use immediately or chill and blend again when needed.
Chocolate Frosting: melt 4 squares unsweetened chocolate, then beat in 1 cup icing sugar, gradually adding 2 tbsp hot water. Beat in 2 eggs, one at a time and 6 tbsp soft butter. Blend until smooth.
To Assemble: sprinkle each cake layer with remaining rum left over after making filling (Mom's note - she uses a bit extra) and spread with Whipped Cream Filling between layers. Coat sides and top with Chocolate Frosting. Pat 1/2 cup walnuts on cake sides. Chill 24 hours before cutting.