Instructions
Prepare the Dough: If making your own rough puff pastry, complete the second refrigeration step. If using store-bought puff pastry, ensure it is thoroughly thawed. Keep the dough refrigerated until ready to assemble the tart.
Prepare the Topping: Heat olive oil in a large skillet over medium-low heat. Add the butternut squash and cook for about 5 minutes, stirring occasionally. Then, add the mushrooms, onion, garlic, salt, pepper, thyme, rosemary, and nutmeg. Continue cooking until the vegetables are tender, approximately 5-6 minutes. Remove from heat and set aside.
Preheat the Oven: Set the oven temperature to 400°F (204°C). Prepare a large baking sheet by lining it with parchment paper or a silicone baking mat.
Assemble the Tart: On a lightly floured surface, roll out the pastry dough into a 10×16-inch rectangle. If using store-bought dough, overlap the edges of the two sheets, then roll them out into the desired shape. Carefully transfer the dough to the prepared baking sheet. If necessary, reshape the dough with your hands. Fold over the edges about 1/2 inch and crimp with a fork. For easier crimping, chill the dough in the refrigerator for 10 minutes before proceeding.
Egg Wash and Layering: Brush the pastry dough with the egg wash, ensuring to coat both the edges and surface. Use a fork to poke small holes in the dough, avoiding the crimped edges. Sprinkle 3/4 cup of parmesan cheese over the dough, followed by the vegetable mixture. Arrange the vegetables evenly across the surface.
Bake the Tart: Place the tart in the oven and bake for 30 minutes. Once done, sprinkle the remaining parmesan cheese on top of the tart. Return the tart to the oven for an additional 5-8 minutes or until the cheese has melted and the pastry is golden brown.
Finish and Serve: Remove from the oven and, if desired, garnish with flaky sea salt, extra pepper, or additional cheese and herbs. Slice and serve warm or at room temperature.
Storage: Leftovers can be stored in the refrigerator for up to five days. To reheat, warm in the microwave or cover and bake at 300°F (149°C) for 10-15 minutes.