Preheat oven to 325 degrees F. Grease and flour 3 (9-inch) round cake pans or spray with flour-added cooking spray and line bottoms with parchment circles.
Have all ingredients measured and ready to go.
Stir baking soda into buttermilk and set aside.
Beat egg whites until stiff peaks form; set aside. I like to do this first and get it over with.
Cream butter, salt (if using) sugar and shortening in bowl of stand mixer for 3-5 minutes. Add egg yolks one at a time, beating well after each addition and scraping the bowl often. Beat in vanilla. By hand or using lowest speed of mixer, add flour and buttermilk mixture alternately to creamed mixture, beginning and ending with flour. Fold in egg whites. When egg whites are incorporated, fold in the pecans and coconut. Batter should be thick and light. Scrape into prepared pans dividing evenly.
Bake at 325 degrees for 25-30 minutes or until cake tests done. My cakes were fairly pale in the center and didn’t appear done, but the cake tester came out clean so I knew they were. Let cool in pans on rack for about 10 minutes, then turn from pans and cool completely.
Cream the butter and cream cheese. Add vanilla. Gradually add powdered sugar. Beat until well blended. Frost the cakes and stack. Garnish with pecans.
This recipe makes enough frosting to frost the cake generously and still have a little extra for decorating.