1/2cup peas (frozen are fine; don’t bother to thaw)
1/2cup chopped fresh parsley, plus a little more for garnish
1 egg
2 tablespoons freshly grated parmesan, plus more for serving (optional)
Instructions
Use a food processor to pulse the flour and salt together. Add the butter and pulse until it is barely blended with the flour, and the butter is broken down to the size of peas. If you prefer to make the dough by hand, combine the flour, sugar, salt, and butter in a large bowl. With your fingertips, two knives or forks, or a pastry cutter, work the butter pieces into the dry ingredients, being sure to incorporate all of the butter evenly until the mixture has the texture of small peas.
Add 4 tablespoons of ice water (not just cold water). Process for about 5 seconds or mix by hand with a wooden spoon, just until the dough begins to clump together, adding 1 to 2 tablespoons more ice water if necessary. Add a little more flour if you add too much water.
Press the dough into a disk about 1 inch thick. It’s important not to overheat, overwork, or knead the dough; squeeze it with enough pressure to just hold it together. Wrap in plastic or put in a zipper bag, pushing out as much air as possible. Freeze for 10 minutes or refrigerate for at least 30 minutes before rolling. (You can make the dough to this point and refrigerate for up to a couple of days or freeze for months. Thaw in the refrigerator overnight before proceeding.) While the dough chills, make the filling.
Heat the oven to 375°F. Put a large, deep skillet over medium-high heat for 2 to 3 minutes. Slice the chicken breasts in half lengthwise (to make them thinner), and sprinkle them with salt and pepper. Put 1/2 cup flour on a plate or in a shallow bowl.
Add the butter and oil to the skillet and swirl it around. When it is hot — a pinch of flour will sizzle — dredge a piece of the chicken in the flour, pressing to coat evenly. Shake it gently, so that excess coating falls off. Add the chicken piece to the pan, then move on to the next one. (Don’t be tempted to dredge in advance and add all the pieces at once; the coating will become soggy, and the heat in the pan will drop too quickly.)
Cook the chicken, regulating the heat if necessary so that there is a constant sizzle but no burning until it’s browned on both sides, about 3 minutes per side. (It’s OK if the chicken isn’t cooked through; it will finish cooking in the oven.) Transfer the chicken to a plate leave the fat in the skillet. Lower the heat to medium. If the pan is too dry, add some more olive oil.
Add the onion, carrots, and garlic to the skillet, and sprinkle with salt and pepper. Cook, stirring frequently, until they just begin to soften, about 5 minutes. Reduce the heat to medium-low and stir in the remaining 3 tablespoons flour; continue cooking and stirring until it just turns tan. Add the chicken stock and cream to the vegetable-flour mixture and turn the heat up to medium. Cook, stirring constantly, and scraping the bottom of the pan, until the liquid begins to bubble and thicken, but don’t let it come to a rolling boil.
Stir in the lemon juice, capers, peas, and parsley, and turn off the heat. Taste and adjust the seasoning with salt and pepper. Chop the chicken into chunks, and stir it into the filling mixture. (Remember, if the chicken isn’t cooked through all the way, don’t taste it).
Before rolling out the dough, pick out the vessel that you’ll use to cook the potpie. An ovenproof skillet, round baking dish, or pie pan will all work; 9 inches in diameter is the ideal size. Dust a large pinch of flour over a clean work surface. Put the dough on the work surface. Sprinkle a little more flour on the dough and dust the rolling pin with flour. (Too much flour will dry the dough; you can always sprinkle on a little more if the dough starts to stick.) Using firm but not too hard pressure on the pin, start rolling the dough from the center outward to form a circle. If the dough feels too hard or is cracking a lot, let it rest for a few minutes. As you roll, only add flour as needed to prevent it from sticking to the pin; lift, rotate, and turn the dough with a spatula to form an even circle. When the dough circle is about 2 inches wider than your baking dish and less than 1/8-inch thick, it’s ready.
Transfer the filling to the baking dish. Beat the egg with 1 tablespoon of water. Brush a little bit of the egg mixture around the outer edge of the dish (this will help the dough stick). Lay the circle of dough on top of the dish, and press the overhanging edges of dough onto the outer sides of the dish, so they stick. Brush the dough all over with the egg mixture, and sprinkle with salt and pepper. Use a sharp knife to cut 3 small vents in the top for the steam to escape.
Put the dish on a rimmed baking sheet, and transfer to the oven. Bake, rotating the baking sheet halfway through, until crust is deeply golden and the filling is bubbling, 50 to 60 minutes. If you like, about 5 minutes before the potpies are done, sprinkle or grate 2 tablespoons of parmesan over the top and continue baking until the cheese is golden and crusty. Sprinkle the potpie with chopped parsley and a little extra parmesan if you like, and serve.