Line a baking sheet with parchment or a Silpat.

Unfold pastry sheet on a lightly floured surface or Silpat. If pastry cracks when unfolding, sprinkle the crack with water and press the edges together to seal. If necessary, use a rolling pin to roll the pastry sheet to 9 inches wide.

Cut pastry sheets into two 9-inch circles. (Use a round 9-inch cake pan as a guide.) Place one puff pastry round on the parchment lined baking sheet and place a sheet of parchment on top. Place the second pastry round on top of the parchment. Put the baking sheet in the refrigerator while you make the frangipane.

Make the frangipane: In a mixing bowl, cream together the butter and sugar on medium speed until light and fluffy, about 3 minutes. Add the almond flour and beat on medium speed until thoroughly blended, about 1 minute. Add the egg and mix on low speed until blended. Add the all-purpose flour, lemon paste, almond extract, and salt, and beat just until combined. Refrigerate until ready to use.

Remove one pastry round from the refrigerator. On a lightly floured surface or Silpat, cut a 1 inch circle / hole in the center of the round. (You can use a piping tip to cut the hole.)

Creating the decorated top: Using a small paring knife, starting from the center of the hole, score a sun-ray decorative pattern on the top of round. You only want to cut through the top layers of the pastry. Don’t cut it all the way through the pastry (I’ve created a template to make this easy). Return pastry to the refrigerator while oven preheats.

Preheat oven to 375°F (190°C).

Remove both pastry rounds from the refrigerator. Place the bottom round on parchment paper or Silpat in the center of the baking tray.

In a small bowl, whisk together the egg yolk and the heavy cream to create an egg wash. Brush a 1-inch border on the bottom round with the egg wash. Be careful not to let the egg wash drip down the sides, which could interfere with the puff pastry rising during baking.

Place the frangipane in the center of the bottom round. Carefully center the top round on top of the frangipane. Use your fingers to gently seal the edges of the top round to the bottom round.

With the back of a knife, score the outer edge of the pastry at regular intervals to create a scalloped edge.

Using a pastry brush, brush the entire top of the pastry with the remaining egg wash. Be careful not to let the egg wash drip down the sides, which could interfere with the puff pastry rising during baking.

Bake until puffed and golden brown, about 45 to 50 minutes.

Transfer Pithivier to a wire rack, and let cool at least at least 1 hour before serving.

Pithiviers are best served the day they are baked. However you can keep it in an airtight container on the counter for up to 2 days. To refresh it, bake it at 300°F (140°C) for 5 to 8 minutes before serving.