Wild Mushroom, Potato and Onion Tart
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It’s no secret we love store-bought puff pastry. It makes quick work of appetizers, doubles as pie crust and can even shortcut a batch of palmiers. (Fancy, right?) This wild mushroom, potato and onion tart (from Melina Hammer’s new cookbook, A Year at Catbird Cottage) proves the freezer staple is essential for quick—not to mention elegant—dinners.
“This tart can serve as breakfast, lunch or dinner and can be eaten hot or room temperature,” she writes. “Good all-butter store-bought puff pastry is something I keep in my freezer so I can throw together a meal just like this without much notice.”
Reprinted with permission from A Year at Catbird Cottage: Recipes for a Nourished Life. Copyright © 2022 by Melina Hammer. Photography Copyright © 2022 by Melina Hammer. Published by Ten Speed Press, an imprint of Penguin Random House.
1 package prepared puff pastry (such as Dufour), thawed in the refrigerator
All-purpose flour, for dusting
12 ounces any fresh wild mushrooms (like a mix of hen of the woods, oyster mushrooms, king boletes or chanterelles)
Extra-virgin olive oil
Full-fat buttermilk, to brush the crust
3 ounces Gruyère, grated
4 medium Yukon gold potatoes, sliced ⅛ inch thick on a mandoline
½ to 1 cup caramelized onions (from about 2 onions)
Leaves from 5 to 9 sprigs fresh thyme
Freshly ground black pepper and flake salt
3 stems fresh tarragon
1. Unfold the pastry onto a lightly floured sheet of parchment and roll to a rough rectangle. With a sharp paring knife, hold the knife edge perpendicular to the pastry and score a border 1 inch in from the edge, all the way around (see Note). Transfer to a sheet pan and chill in the refrigerator while you prepare the toppings. Preheat the oven to 400°F.
2. Slice the mushrooms into ¼-inch pieces. In a large cast iron skillet, cook the mushrooms with a drizzle of oil and a pinch of salt until they begin to collapse and brown, 5 to 7 minutes, turning occasionally. Remove the pan from the heat and set aside.
3. Take the pastry out of the fridge. With a pastry brush, brush the buttermilk onto the border.
4. Sprinkle the Gruyère in an even layer onto the pastry, inside the border. Arrange the potato slices like shingles, followed by the caramelized onions, scattered around. Sprinkle half the thyme leaves, then add the mushrooms, followed by the remaining thyme leaves. Season with pepper and drizzle a very small amount of oil, just enough to kiss the surface in places.
5. Bake the tart on the sheet pan until the pastry is golden and the cheese is melted, 25 to 30 minutes, rotating the pan after 20 minutes. Cool the tart on a wire rack for 5 minutes.
6. Cut into slices, season with flake salt and freshly ground pepper to taste and sprinkle with fresh tarragon leaves for garnish. Store any leftovers between layers of parchment, sealed in a container in the refrigerator, for up to 3 days. Reheat slices in a moderate oven or toaster oven for best results.
Note: Scoring a border helps puff up the crust as the butter within the laminated pastry melts, expanding the layers in the roaring hot oven.