• First, you need to decide which puff pastry you’re going to use. You can use store-bought puff pastry if you’re in a hurry, or make your own as I did here, following my Rough Puff Pastry recipe. If you choose to make it yourself, prep it in advance and let it chill in the fridge overnight, it makes the pastry easier to handle and results in even flakier layers.

Prepare the vanilla pastry cream.

• Place milk in a medium saucepan and bring to a simmer.
  
• Meanwhile, whisk the egg yolks with sugar and salt until well combined.
  
• Add flour and cornstarch and mix to combine.
  
• Gradually add milk to the egg mixture.
  
• Return to heat.
  
• Cook, stirring constantly until it boils and thickens.
  
• Remove from heat and add vanilla extract.
  
• Pour the cream into a clean bowl.
  
• Cover it with plastic wrap, and press the wrap directly onto it's surface to prevent a skin from forming.
  
• Let it cool to room temperature. You can also prepare it a day in advance and refrigerate it overnight.

Assemble the tart.

• Preheat the oven to 400°F (200°C).
• Transfer the puff pastry onto a floured parchment paper.
  
• Roll the puff pastry into a rectangle, about 12×14 inches (30×35 cm). (Store-bought puff pastry comes already rolled.
  
• Cut about 1-inch (2cm) strips from all four edges.
  
• Brush with beaten egg.
  
• Place these strips back onto the edges of the rectangle to create a raised border to hold the pastry cream.
  
• Prick the center, inside the border, all over with a fork.
  
• Brush the pastry border with beaten egg.
  
• Bake at 400°F (200°C) for 10–12 minutes, until puffed and just beginning to color.
  
• Let the pastry cool slightly.
• Meanwhile, cut the apple into thin slices.
  
• Add the vanilla pastry cream inside the baked shell.
  
• Spread it evenly.
  
• Arrange the apple slices neatly on top. Brush the edges again with beaten egg for extra color. This is optional.
  
• Bake again at 400°F (200°C) for 20–25 minutes, until the apples are tender and the pastry is golden.
  
• While still warm, brush the apples with warm apricot jam or a simple sugar syrup for a glossy finish.
  
• Let it cool slightly. Here you can see how nicely the pastry puffed
  
• Dust the edges with powdered sugar. Enjoy!