Preheat oven 350 degrees F.
Sift flour with baking powder, baking soda, and salt.
With mixer at medium speed, beat Butter until very soft and creamy; gradually beat in ¾ cup sugar, beating until light and fluffy. Beat in egg yolks, one at a time, then orange peel.
Combine orange juice with 3 tablespoons rum and extracts; at low speed, add to butter mixture alternately with flour mixture, while beating at low speed.
In a medium bowl, beat egg whites until soft peaks form; gradually beat in ¼ cup sugar, continuing to beat to stiff peaks.
Fold batter into whites; then pour into pans. Bake 25 minutes, or until top springs back when gently pressed with finger. Cool in pans on wire racks, 10 minutes, then remove from pans to finish cooling. Meanwhile, make WHIPPED -CREAM Filling.
With long, sharp knife, split cooled layers horizontally to make 4 layers in all. Sprinkle each cake layer with 2 tablespoons WHITE rum. On cake plate, put layers together using about 1 ½ cups Whipped-Cream Filling between every two (2) layers. Refrigerate cake while making Chocolate Frosting - Use to frost front sides and top of cake, then press walnuts all around sides of cake. Refrigerate cake at least 18-hours before serving time.