In a small bowl, mix cornstarch with 1/2 cup milk.In a medium-size saucepan, over moderate heat, heat remaining 1 1/2 cups milk.
When milk is just under boiling, add peanut butter, honey, and salt.
Mix thoroughly, then stir in cornstarch mixture and continue cooking about 5 minutes, until thick and creamy.
Pour about 1/2 cup of the hot mixture into the beaten egg, then return this mixture to the saucepan and cook 1 minute longer.
Remove pan from heat, add vanilla, and beat about 1 minute.
Pour into individual dessert dishes, cover, and refrigerate several hours before serving.