Beat butter and shortening at medium speed with an electric mixer until fluffy; gradually add sugar, beating well. Add egg yolks, one at a time, beating until blended after each addition. Add vanilla; beat until blended.
Combine flour and soda; add to sugar mixture alternately with buttermilk, beginning and ending with flour mixture. Beat at low speed until blended after each addition. Stir in 1 cup flaked coconut.
Beat egg whites until stiff peaks form; fold into batter. Pour batter into 3 greased and floured 9-inch round cake pans.
Bake at 350° for 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks for 10 minutes; remove from pans, and cool completely on wire racks.
Spread 3/4 cup chilled Fresh Orange Curd between layers; spread remaining Fresh Orange Curd on top of cake. (The Fresh Orange Curd layer on top of cake will be very thick.) If desired, loosely cover cake, and chill 8 hours. (Chilling the cake with the curd between the layers helps keep the layers in place and makes it much easier to spread the frosting.) Spread 3 cups Pecan-Cream Cheese Frosting on sides of cake, reserving remaining frosting for another use. Sprinkle 1/2 cup toasted coconut over top of cake, if desired. Note: Cake may be frosted with Pecan-Cream Cheese Frosting immediately after adding the Fresh Orange Curd, but the cake layers will not be as steady.