In a large bowl, combine the first five ingredients. Beat on low until for 30 seconds. Beat on medium for 2 minutes.
Pour into a greased and floured 10-in. fluted tube pan. Bake at 350° for 40-45 minutes or until a toothpick inserted in the center comes out clean. Cool for 10 minutes before removing from pan to a wire rack to cool completely.
For sauce, in a small saucepan, combine the sugar, cornstarch and salt; gradually stir in milk. Bring to a boil over medium heat; boil for 1-2 minutes, stirring constantly. Stir a small amount of hot filling into egg yolk; return all to pan, stirring constantly. Bring to a gentle boil; cook and stir 2 minutes longer.
Remove from the heat; stir in butter and vanilla. Cool for 15 minutes. Fold in whipped cream. Store in the refrigerator. Serve with the cake.