In a medium size bowl, whisk the egg yolks with 1/4 cup of the milk, sugar, vanilla and cornstarch.
In a sauce pan, heat the milk until it's hot, but not yet boiling. Take the milk off the heat and slowly start adding the egg mixture to the hot milk, while continuously whisking. Continue adding egg mixture and whisking until all the egg mixture is gone. Place the sauce pan over the heat again and which until the mixture thickens and resembles custard.
Remove from heat and cool.
Preheat oven to 375 F degrees.
Roll out the puff pastry into a long piece that's about 18 inches long and 6 inches wide.
Using the tip of a sharp knife, mark a shallow cut 1/2 inch from the edge of the pastry to form a rim.
Spread half of the custard onto the pastry, keeping the custard inside the marked rim.
Arrange strawberries nicely on the custard.
Sprinkle with sugar and bake for 20 to 25 minutes.