This was one of my favorite tradition growing up. Every year for the Epiphany, my mom would make this cake and we would celebrate together eager to know who would be crowned king or queen... She gave me the recipe and I gladly pursue this every year with my kids and still enjoy it so much! —Virginie Degryse
Preheat the oven to 350 degrees. Mix in the flour with the butter, add 1 egg and mix until the mixture becomes light and creamy. Do not overmix or the gluten in the flour will overdevelop and the almond cream will lose its delicate texture when baked.
Cut the puff pastry dough sheets into 2 9-inch circle. Place 1 of the circles on a parchment paper-covered baking sheet. Spoon the almond cream in the center of the circle. The mound should be about 1-inch high, leaving a 2 inch border clear.
Mix the milk and egg for egg wash. Lightly brush the remaining 1 1/2-inch rim of the pastry circle with the egg wash. Place the second circle of puff pastry over the first. Gently press against the sides of the almond cream mound to remove any trapped air. Seal the edges of the 2 layers by pressing the top edge into the bottom edge. This will keep the almond cream from running out as it bakes. Use a sharp knife to give the circle a fluted edge, this will allow steam to escape during baking.
Bake the pithiviers until it begins to brown slightly, about 20 minutes. Lower the oven 20 degrees and continue to bake until well risen and evenly browned, about another 15 minutes. The pithivier is best when served while it is still slightly warm. Use a serrated knife to slice it.