For the Crust:

1. 1. Preheat your oven to 400°F (200°C).
2. 2. Roll out the thawed puff pastry on a floured surface to fit your tart pan. Press into the pan and trim any excess pastry hanging over the edges.

For the Filling:

1. 1. In a skillet over medium heat, melt 1 tablespoon of butter. Sauté sliced mushrooms until golden brown and tender, about 5-7 minutes. Season with salt and pepper.
2. 2. In a mixing bowl, combine fresh pumpkin puree, sautéed mushrooms, chopped sage leaves, eggs, and heavy cream. Whisk until smooth.
3. 3. Pour the pumpkin mixture into the prepared crust and spread it evenly.
4. Baking:
5. 1. Bake in the preheated oven for 30-35 minutes or until the filling is set and the top is golden brown.
6. 2. Allow to cool slightly before slicing. Serve warm or at room temperature.