Grease and flour two round cake pans or one large pan for a single layer cake.
Sift together flour, baking powder, baking soda and salt.
Cream shortening. Beat in 1 and 2/3 cups sugar. Blend in vanilla and coconut extracts. Beat in egg whites.
Blend in flour alternately with buttermilk, beginning and ending with flour mixture. Using a mixer, beat on low for 2 minutes. Pour into pans. Bake at 350 degrees for 25 to 30 minutes or until a toothpick tests clean.
Cool 10 to 15 minutes in pans, then finish cooling on racks. Cool completely before frosting.
For frosting: Put Wondra in saucepan. Slowly blend in milk. Cook over medium heat, stirring, until thick. Cool.
In deep bowl, beat butter, shortening and salt. Beat in confectioner's sugar and vanilla. Beat in cooled white sauce until fluffy.
Frost cake. Sprinkle with all of the coconut.
Store in refrigerator.
Cooking time does not include the time for the cake and frosting to cool.