Time: 90 minutes
12 ounces mixed mushrooms (such as maitake, yellow oyster, blue oyster, shiitake, and/or royal trumpet), torn or sliced into 2” pieces
5 Tbsp. extra-virgin olive oil, divided, plus more for brushing phyllo
2 large sprigs thyme plus 1 tsp. chopped fresh thyme leaves
1 tsp. Diamond Crystal kosher salt, plus more
5 garlic cloves, peeled
1 large yellow onion, thinly sliced
1 tsp. sherry or red wine vinegar
1⁄2 bunch Swiss chard or Tuscan kale, ribs and stems removed, thinly sliced crosswise (about 2 packed cups)
Freshly ground black pepper
Pinch of crushed red pepper flakes
1⁄2 tsp. finely grated lemon zest
1 large egg, beaten
1⁄2 cup heavy cream
3 ounces Gruyère, finely grated (about 1 cup)
12 sheets frozen phyllo pastry, thawed (from half of a 1-lb. package)
Step 1 - Place a rack in center of oven; preheat to 425° F. Toss mushrooms, 3 Tbsp. oil, thyme sprigs, and 1 tsp. salt in a large bowl. Arrange mushrooms in
a single layer on a rimmed baking sheet.
Step 2 - Place garlic cloves in the center of a small square of aluminum foil. Drizzle garlic with olive oil, then fold oil into a packet and add to baking sheet.
Roast mushrooms and garlic until mushrooms are browned and garlic is soft, about 20 minutes, turning mushrooms once after 15 minutes. Mash cloves with
a fork and set aside. Reduce oven to 400°F.
Step 3 - Heat 2 Tbsp. oil in a 10” ovenproof skillet over medium-high heat. Add onions and cook, stirring occasionally and reducing heat as needed to prevent
burning, until onions are deep golden brown and jammy, about 20 minutes. Add vinegar to skillet and scrape up browned bits with a wooden spoon. Add a
handful of greens and cook, stirring, until bright green and wilted, about 30 seconds. Repeat with more handfuls of greens until everything is wilted; season
with salt and pepper. Add chopped thyme and pepper flakes and cook, stirring, another 30 seconds. Transfer onion mixture to bowl with mushrooms and add
mashed garlic and lemon zest; stir to combine.
Step 4 - Add egg, heavy cream, and Gruyère to mushroom mixture, season with pepper, and stir to combine.
Step 5 - Brush skillet with a thin layer of olive oil. Working quickly but carefully, lay two sheets of phyllo on a work surface and lightly brush them with oil. Overlap phyllo sheets to cover the bottom and sides of the pan (there should be some overhang). Repeat with remaining phyllo sheets. Evenly spread the mushroom mixture over phyllo. Fold phyllo overhang over filling, leaving center exposed, and gently brush overhang with oil.
Step 6 - Cook pie over medium heat until bottom of pastry is just golden, about 3 minutes. Transfer skillet to oven and bake pie until phyllo is golden brown and crisp and filling is set, 25–30 minutes. Let pie cool in skillet at least 15 minutes before slicing. Serve warm.