Preheat oven to 425 F and spray a 9-inch pie plate with cooking spray; set aside.: The oven should be fully hot so the pie crust begins to set the moment it enters, producing a crisper bottom and a golden top. You will notice the kitchen warming and the anticipation building. If you skip preheating the crust can turn soggy because the filling will release steam before the pastry begins to bake, so always wait for a full preheat.
Peel and cube the potatoes, place them in a microwave-safe bowl, cover with 1 tablespoon water, cover the bowl with plastic wrap, and microwave on high for 5 minutes. Tip– This allows the potatoes to head start on cooking before placing them in the pie with the other ingredients which are faster cooking.: The potatoes should emerge steaming and slightly tender at the edges, with a faint starch scent that hints they are nearly done. This jump start shortens skillet simmer time and prevents uneven cooking in the pie. If they are still very firm, give them another minute in the microwave; avoid overcooking or they will dissolve in the filling.
While the potatoes are microwaving, to a large skillet, add the butter, carrots, onion, celery, and sauté over medium-high heat for about 4 to 5 minutes, or until vegetables begin to soften; stir frequently.: You will hear a steady sizzle and see the onion turn translucent while the carrots and celery soften. This step builds a sweet, savory base that flavors the entire filling, and stirring prevents sticking and uneven browning. If your pan smokes, reduce the heat slightly, because burned butter will impart a bitter note.
Add the garlic, stir to combine, and sauté for 1 minute or until fragrant; stir constantly.: The scent of garlic will bloom quickly into the air, brightening the sauté. Keep it moving so it turns fragrant without browning, which can bring a sharp, bitter edge. If you smell bitterness, you've likely overcooked the garlic ; remove the pan from heat briefly to cool and carry on.
Evenly sprinkle the flour and cook for about 3 minutes, or until the flour is well toasted since it will combine with the butter to give a foundational level of flavor to the pot pie, meaning you want it browned a bit.: As the flour cooks, it will stop smelling raw and take on a warm, toasty aroma, forming the roux that thickens your gravy. Stir constantly to avoid lumps and to develop that slightly nutty flavor. If you still detect raw flour taste later, it means the roux needed more toasting time.
Add the broth, microwaved potatoes (drain any excess water before adding them), thyme, salt, pepper, stir to combine, and allow the mixture to simmer over medium heat for about 10 minutes, or until the potatoes and carrots are tender.: When the broth hits the roux the mixture will bubble and thicken, releasing savory steam and deep aromas. The simmer softens the vegetables and integrates flavors. Keep an eye on bubbles, and stir occasionally to prevent the base from sticking. If the sauce is too thin after simmering, continue to reduce gently until the vegetables are tender and the liquid coats a spoon.
Add the milk, peas, corn, and simmer over medium-low heat until the gravy thickens while you prepare the crust.: The addition of milk will soften the color and lend creaminess, while the peas and corn add sweetness and color. As it simmers you should see the gravy thicken to a glossy coat on a spoon, and hear a quieter simmer as the heat lowers. If the filling becomes too thick, loosen with a splash of extra broth or milk .
Roll out the store bought or homemade pie crust to fit your 9-inch pie pan.: The dough should feel cool and slightly tacky, and rolling will produce a uniform thickness that bakes evenly. Use a light dusting of flour to prevent sticking, and turn the dough periodically to maintain an even circle. If the dough cracks, press it gently and chill briefly before finishing to avoid a broken crust.
To place the crust in the pie pan use a lightly floured rolling pin and roll the pie crust onto the rolling pin, place over the 9 inch pie pan and unroll the rolling pin so that the crust is centered over the pie pan; set aside.: This method keeps the crust intact and centered, and you will feel the dough settle into the pan as you unroll. Make sure the edges are even for a tidy finish. If the crust slips, press it gently and refit, chilling briefly if it becomes too soft.
Remove the skillet that’s been simmering from the heat and add the shredded leftover turkey, chicken, rotisserie chicken, etc. Stir to combine.: The residual heat will warm the turkey without overcooking it, and you will see the meat glisten as it absorbs the gravy. Stir gently to distribute the protein evenly so each slice has balance. If the turkey is dry, a touch more gravy or a splash of warm broth will revive it.
Taste the mixture and if you think it needs more salt, pepper, thyme, etc. add it now, to taste.: This is the moment to balance flavors, and you should sample a spoonful warm to judge seasoning. Adjusting now ensures the finished pie is seasoned correctly after baking. If you oversalt, a squeeze of lemon or a few spoonfuls of unsalted milk can help mellow the saltiness.
Gently spoon the mixture into the pie plate on top of the pie crust.: As you spoon the filling in, you will feel its weight settle into the shell and hear a quiet plop. Leave a bit of room under the rim so the top crust can seal without overflowing. If the filling is too full, it may bubble over during baking, so remove a couple of spoonfuls to avoid mess.
Now you will prepare to place the top pie crust over the top but first cut out 4 to 5 small slits into the top of the pie dough with a sharp knife so the steam can be released as the pie cooks. A star-shape is what I did for this pot pie.: The slits should be neat and intentional, and when cut you will see steam vents that ensure even baking. Decorative vents also let steam escape so the filling does not push the crust off. If you skip vents, the pie may bubble and crack unpredictably.
Place the top pie crust over the top and crimp the edges of the pie dough by pinching the top and bottom of the dough together between your fingers, and repeat all along the edges of the pie to seal. Tip– For good measure as a steam valve, prick the very center 5 or 8 times with the very tip of a sharp paring or small knife.: Proper sealing keeps the filling contained and creates a neat edge that browns evenly. You will see the edges come together and form a pleasing ridge. Poorly sealed edges can open while baking, so press firmly and chill if the dough becomes too soft.
Place the pie dish on a baking sheet, and put the whole thing in the oven. Tip– The baking sheet will catch any bubble-overs that occur as the pie bakes so it doesn’t burn on the bottom of your oven (less potential cleanup for you).: The baking sheet is a small protective step that saves cleanup and prevents smoky oven aromas. Slide the sheet onto the middle rack and listen for the first, gentle crackle as the crust starts to bake. If you omit the sheet, a bubbling spill can caramelize on the oven floor and cause smoke.
Bake for 35 to 40 minutes, or until the crust is golden brown, and the filling is bubbling (you will be able to see it because of the slits you made in the top crust). Check pie at 25 minutes and if it seems that the crust is browning too quickly, either drape a sheet of foil loosely over the top (tenting the pan) or carefully apply strips of foil around the edges of the crust only to shield it from browning.: Toward the end of baking you will hear the faint bubble and see the top turn a warm amber hue. This caramelization adds flavor and texture. If the edges brown too fast, shielding them prevents burning while the rest finishes. If the filling is not bubbling near the vents, bake a little longer, as that bubbling is a sign the center has come fully to temperature.
Serve immediately. Pie will keep airtight in the fridge for up to 5 days and in the freezer for up to 3 months, noting that the crust of the leftovers will not be as flaky and light.: When you cut into the pie you should see glossy, steaming filling and a crisp crust. Letting it rest for five to ten minutes will make slicing cleaner, but warm serving delivers the best texture. If freezing, wrap tightly and reheat at moderate oven heat to revive the crust; microwaving will soften it.