Combine soda and buttermilk and set aside.
In a mixing bowl cream sugar, butter and shortening until light and fluffy.
Add egg yolks one at a time. Beat well after each addition.
Add buttermilk and flour a little at a time.
Stir in vanilla. Set aside.
In another mixing bowl beat egg whites until stiff, but not dry.
Gently fold the egg batter into the egg whites making sure everything is mixed.
Add the coconut and nuts.
Pour into the 3 prepared 8-inch cake pans.
Bake at 325 F for 30 minutes or until a wooden toothpick poked into the middle of the cake comes out clean.
Let the pans cool on wire racks for 10 minutes; remove from pans, then cool completely on wire racks sprayed with cooking spray to prevent sticking.
Icing
With an electric mixer beat the cream cheese with the butter on high speed until fluffy.
Reduce the speed and blend in the powdered sugar, vanilla and coconut extract.
Beat well until it is smooth and light.
Fold in the toasted pecans.
Spread the frosting between the layers and on the sides and top of the cake.
Sprinkle with the toasted coconut.