Vegetable pot pie on a baking sheet

Ingredients:

Dough

• 1 and 3/4 cups of premium flour + extra for working with the dough
• 2 tbsp. l. grated parmesan
• 1 tbsp. granulated sugar
• 2 tbsp. chilled shortening
• 6 tablespoons chilled unsalted butter, cut into small pieces
• 1 large egg, lightly beaten
• 2-4 tablespoons of ice water

Filling

• 2 x 280g packages of sliced ​​brown cremini mushrooms
• 3 tablespoons extra-virgin olive oil
• 900 g celery root, parsnip and/or turnip, peeled and cut into 2.5 cm pieces.
• 3 carrots, peeled and cut into 2.5 cm pieces (cut thick ones in half lengthwise)
• Half a fennel root, cut into thin slices lengthwise
• 2 shallots, each cut into 6-8 pieces
• 1 teaspoon chopped fresh rosemary
• 1 and 2/3 cups mushroom or vegetable broth
• 0.5 cups heavy cream
• 1 cup frozen green peas

Preparation:

1. Dough:
   
   In a food processor, combine the flour, Parmesan, sugar, and 1/2 teaspoon each fine salt and black pepper. Add the chilled shortening and pulse until the mixture resembles coarse grains. Add the butter and pulse until the mixture forms pea-sized pieces. Add 2 tablespoons of the beaten egg (reserve the rest) and 2 tablespoons of ice water; pulse a few times until the dough begins to come together, adding a little more water, 1/2 tablespoon at a time, if necessary. Transfer the dough to a piece of plastic wrap, form into a rectangle, wrap tightly, and refrigerate to set for at least 1 hour or overnight.
2. Meanwhile, prepare the filling.:
   
   Preheat oven to 450°F (230°C). Toss the mushrooms on a rimmed baking sheet with 1 tablespoon olive oil and a pinch of coarse salt, season with pepper to taste. Roast until the mushrooms are shriveled and release some liquid, 8 to 10 minutes. Add the celery root, parsnips and/or turnips, carrots, fennel, shallots, rosemary, 1 teaspoon coarse salt, 1/2 teaspoon black pepper, and the remaining 2 tablespoons olive oil; toss to combine. Roast until the vegetables are tender and the mushroom liquid has evaporated, about 30 minutes.
3. Lightly flour a sheet of parchment paper. Roll out the dough on the parchment paper into a 30x35 cm rectangle. Refrigerate while the vegetables bake.
4. Pour 2/3 cup of broth into the baking sheet, especially into the corners, and scrape up any browned vegetable bits. Add the remaining 1 cup of broth, heavy cream, and green peas.
5. Cut the dough into 2-cm-wide strips. Lay half of the strips diagonally across the vegetables, trimming or adding pieces as needed. Lay the remaining strips on top in the opposite direction. Brush the dough with the remaining beaten egg. Bake until golden brown and the liquid has thickened, 25-30 minutes. Let cool for 5 minutes before serving.