Sift flours, BP and salt. Stir with whisk to mix thoroughly.
Add egg whites and flour mixture to egg yolk mixture alternating each and folding until batter is just incorporated.
Batter will have some traces of flour exposed. Do not stir and do not over mix for best results.
Grease 2 9 cake pans. Line bottom of each with waxed paper or parchment. Grease paper and dust bottoms and sides with flour.
Bake at 350 for approximately 30 minutes. Test for doneness with toothpick.
For ease in slicing the layers in 2, place cake layers in pans in freezer. To remove from pan when ready to assemble, turn stove burner to med and slide bottom of cake pan around until the heat releases cake; test by using a butter knife pulling the sides up until cake comes free from bottom.This happens within seconds. Slice frozen layers in two and spread filling between layers leaving top of cake bare.
Cream egg yolks.
Mix cornstarch with a small amount of the milk and then add to saucepan with balance of milk, creamed egg yolks and sugar. Cook until it comes to a boil.
Remove from heat and add butter and vanilla.
Can use leftover egg whites to frost sides of cake with 7 minute frosting.