Prepare the custard filling: Heat the milk, but make sure it does not come to boil. In the mixer bowl, beat the egg yolks and sugar until they are turn fluffy and white. Gradually add the flour and lemon zest while beating and, finally, slowly add the hot milk. Transfer the mixture into a saucepan and stir constantly over medium heat until it starts to thicken. When thick, pour the lemon juice and stir until all ingredients are combined to a creamy consistency. Empty the custard into a bowl and allow to cool in the refrigerator without covering. Just before serving, whip the crème fraîche until thick and firm, and softly combine it with the lemon filling. To serve, use a pastry sheet as a base, spread over some of the filling, cover with another sheet and repeat. Brush the last sheet with a little cream, sprinkle with ice sugar, cut into portions and serve. Keep the remaining mille-feuille in the freezer until the next time you wish to serve it. Let it thaw at room temperature for about 1 hour. This way, you can make sure the puff pastry sheet remains crispy.

For making Mille-feuille Bases:
Lay the pastry sheet on the flat surface of a baking tin and make small holes all over its surface with a fork. Beat the egg with 1 tablespoon of water and brush its surface. Sprinkle with a little sugar and bake in a preheated oven at 190°C for 30 minutes. Let it cool down and cut lengthwise into 3 strips.
Prepare the custard filling: Heat the milk, but make sure it does not come to boil. In the mixer bowl, beat the egg yolks and sugar until they are turn fluffy and white. Gradually add the flour and lemon zest while beating and, finally, slowly add the hot milk. Transfer the mixture into a saucepan and stir constantly over medium heat until it starts to thicken. When thick, pour the lemon juice and stir until all ingredients are combined to a creamy consistency. Empty the custard into a bowl and allow to cool in the refrigerator without covering. Just before serving, whip the crème fraîche until thick and firm, and softly combine it with the lemon filling. To serve, use a pastry sheet as a base, spread over some of the filling, cover with another sheet and repeat. Brush the last sheet with a little cream, sprinkle with ice sugar, cut into portions and serve. Keep the remaining mille-feuille in the freezer until the next time you wish to serve it. Let it thaw at room temperature for about 1 hour. This way, you can make sure the puff pastry sheet remains crispy.

For making Mille-feuille Bases:
Lay the pastry sheet on the flat surface of a baking tin and make small holes all over its surface with a fork. Beat the egg with 1 tablespoon of water and brush its surface. Sprinkle with a little sugar and bake in a preheated oven at 190°C for 30 minutes. Let it cool down and cut lengthwise into 3 strips.