Prepare the Pastry:

In a bowl, combine flour and salt. Add butter and mix until the mixture resembles coarse crumbs. Gradually add ice water until the dough comes together. Form into a disk, wrap in plastic, and chill for at least 1 hour.

Pre-bake the Crust:

Preheat the oven to 375°F (190°C). Roll out the dough to fit a 9-inch tart pan. Press into the pan, trim the edges, and prick the bottom with a fork.
Line with parchment and fill with pie weights. Bake for 15 minutes, remove weights and parchment, and bake for another 5 minutes.

Prepare the Filling:

In a skillet, heat olive oil over medium heat. Sauté mushrooms, garlic, shallot, and thyme until mushrooms are browned and tender. Season with salt and pepper. Let cool.

Assemble the Tart:

In a bowl, whisk together crème fraîche, eggs, and cheese. Stir in the mushroom mixture. Pour into the pre-baked crust.

Bake the Tart:

Bake at 375°F (190°C) for 25-30 minutes or until the filling is set and the top is golden.

Serve:

Garnish with fresh parsley. Serve warm or at room temperature.