Separate eggs whites from yolks. In a medium sized bowl, combine egg yolks, sugar, and cornstarch, and whisk until pale yellow.
In a medium saucepan, combine milk and vanilla paste and bring to a simmer stirring to ensure milk doesn't burn on the bottom of the pan.
When milk comes to a soft boil, stir half the milk mixture into the egg mixture, whisking to ensure the eggs don't scramble, then return the mixture to saucepan.
Stir the custard until it thickens and remove from heat. Place in a bowl and cover the surface with saran wrap. Refrigerate until ready for use.