Roll out the puff pastry to fit your pie dish, ensuring it covers the bottom corners. Prick the pastry with a fork.

Peel the potatoes and finely slice the shallot. Use a mandolin to slice the potatoes very thinly.

Sprinkle salt over the potatoes and let them sit for 10 minutes to draw out moisture. Afterward, strain the potatoes and place them on a towel to dry.

Layer the potatoes in the pie dish, followed by a layer of shallot and a sprinkle of fresh thyme. Repeat these layers until you reach the top, finishing with a layer of potatoes and more thyme.

Roll out the second piece of puff pastry to cover the top of the pie. Crimp the edges to seal and trim any excess pastry.

Cut a small hole in the center of the top pastry and pour in a bit of heavy cream, using your finger to lift the pastry and allow more cream underneath.

Brush the top with egg wash and bake in a preheated oven at 350 degrees for about 45 minutes.

While the pie bakes, prepare the cream mixture by combining creme fraiche and heavy cream.

Check the potatoes for doneness by inserting a knife. Once cooked, remove the top pastry and spread the cream mixture over the potatoes, allowing it to soak in.

Replace the puff pastry lid and return the pie to the oven for an additional 15 minutes.

After 15 minutes, check that the cream is bubbly and golden. Garnish with thyme leaves in the center before slicing.