Preheat your oven to 350°F (175°C).

Take out the puff pastry sheets from the package and let them thaw at room temperature for about 10-15 minutes.

Grease a 9x13 inch baking dish with butter or cooking spray.

Place one of the pastry sheets at the bottom of the baking dish.

In a large mixing bowl, whisk together egg yolks and sugar until pale and fluffy.

Add the flour and continue to whisk until the mixture is smooth.

Slowly add the milk and whisk until everything is combined.

Pour the custard mixture into a large saucepan and cook over medium heat, stirring constantly until the mixture thickens and coats the back of a spoon (about 10-15 minutes).

Remove from heat and stir in the vanilla extract.

Pour the custard mixture over the bottom pastry sheet in the baking dish.

Place the second pastry sheet on top of the custard mixture.

Beat the heavy cream until stiff peaks form and spread it evenly over the pastry sheet.

Bake for about 35-40 minutes or until the pastry is golden brown.

Remove from the oven and let it cool to room temperature.

Once cooled, refrigerate for at least 2 hours before slicing and serving.