Roasted Potato Tart with Sauteed Mushrooms & Gruyere
Adapted from Once Upon a Tart
Crust can be made a day ahead….total time 90 minutes
Final roasting and baking …90 minutes
Servings: 4 dough makes enough for 2 9" crusts
Crunchy Savory Tart Crust modified slightly – this recipe makes enough for 2 – 9” tarts:
2 cups all purpose flour (the book calls for 2 ½ cups, but it kept crumbling for me)
3 tbsp semolina flour
1 tsp salt
12 tbsp (1 ½ sticks) cold unsalted butter, cut into ¼” pieces
3 tbsp cold solid vegetable shortening (I used Crisco)
Ice cold water (they suggest starting with 4 tbsp and then adding by the tbsp as needed. I ended up using a little more than half cup – double what they said
1 lb/450g red skinned potatoes, scrubbed and cut into ½” disks
1 medium yellow onion, diced
¼ cup olive oil
2 large cloves garlic, peeled and minced
2 tsp fresh tarragon, chopped (I’m not a tarragon fan, so I used rosemary. Thyme would be awesome too)
4 large eggs
1/2 cup light cream
Salt & pepper
1 -1½ lb/450-700g mushrooms, thinly sliced (I used shitake & cremini)
½ heaping cup Gruyere cheese, coarsely grated
1. Put the flours and salt in the bowl of the food processor fitted with the metal blade. Pulse a couple of times to combine the flours and salt.
2. Add the chilled butter and shortening and pulse - until the mixture looks like “moist crumbs” (I’m not sure what that looks like exactly, but don’t allow it to come to a paste) .
3. This step is where I had difficulty. I usually over mix and make a tough dough, so this time – twice in fact, I didn’t add enough water and it was too crumbly to roll. I took some liberties a la Barefoot Contessa, Instead of turning the flour/butter mixture into a large bowl and adding tablespoons of water and mixing by hand….I added ½ cup of water through the feeding tube and pulsed until it started to form a ball. I then gathered it into a ball (actually split the dough into two portions.
4. Wrap each ball, flattened to a disk, in plastic wrap and refrigerate for 30 minutes or longer.
5. Roll the dough on a lightly floured surface, about 2” larger than the circumference of the 9” tart pan (with a removable bottom). Fold over the rolling pin and place in the tart pan, gently fitting the pastry up the sides, flush with the bottom. Remove any excess pastry from the top.
6. Refrigerate for another 30 minutes before baking in the center of the oven. Preheat oven to 400°F/ 200°C . All this refrigerating , makes sure the butter is cold so that when it hits the heat of the oven, it will make the flakiest crusts imaginable.
7. Use a fork to prick holes over the bottom of the pie shell. Place a sheet of parchment paper (larger than the tart pan) over the pie crust and cover with pie weights (I used dried beans – just save them for the next pie and remember not to use them for cooking) and bake for 10 minutes. Remove the weights and return the tart to the oven and bake for another 5-10 minutes or until the crust is golden brown.
8. Remove from the oven and allow to cool.
Filling & Final Baking:
1. Preheat oven to 450°F/ 220°C
2. In a large bowl, toss the potatoes with half the olive oil, onions, garlic, salt & pepper. Lay in a single layer on a rimmed baking sheet, lined with parchment and roast for until golden and fork tender (about 15 minutes, turning midway). Remove from the oven and allow to cool slightly before filling the pie shell.
3. Reduce the oven temperature to 375°F/ 190°C . Sprinkle the tart shell with chopped herbs and place the potato slices and onions evenly over the crust.
4. In a medium bowl or large measuring cup, whisk the eggs. Add the cream and pepper and pour over the potatoes…this is your "custard". Only use as much as your pan will allow and …for easy cleanup, bake your tart on a rimmed baking sheet.. There should be some crust exposed. Bake for 55-60 minutes or until the custard (egg mixture) won’t jiggle and is firm.
5. In the meantime, Heat the rest of the olive oil in a non-stick skillet over medium high heat. Add the mushrooms and sauté until golden…about 5 minutes.. Remove from heat.
6. Top the tart evenly with the grated cheese and then add the mushroom mixture to cover the cheese. Return to the oven for 5-10 minutes (until the cheese melts).
7. Remove the tart from the oven and allow to cool on a wire rack for about 5 minutes before removing the outer part of the pan. The easiest way to remove the tart…great tip from the authors…is to place the entire pan on a large can and allow the outside ring to fall. Place the tart on a work surface and slide off the metal onto a serving plate.
This dish can be served warm or at room temperature. The simplest salad makes a complete meal. ( Toss some arugula with a drizzle of good quality olive oil and some balsamic apple cider vinegar). Also great as part of a buffet brunch or picnic supper.