Combine sugar, cornstarch, and salt in a small saucepan. Stir in milk. Cook over medium heat, stirring constantly, until mixture comes to a boil. Boil for 1 minute before removing from heat. Stir a few tablespoons of the hot mixture into the beaten egg yolk. Pour the egg mixture back into the hot milk mixture. Bring mixture back to a boil. Remove from heat and add vanilla. Cool mixture to room temperature. Cover with plastic wrap and chill until set.
YUMMY! My husband's boss asked me to make a cake at the last minute.... anything I felt like making. I didn't want to fill with buttercream so I decided to try this and it's so good! I just want to eat it right out of the bowl!