Chicken Pot Pie

For the crust:

1 1/4 cups all-purpose flour, plus more for work surface 
1/2 teaspoon sea salt 
1/2 cup (1 stick) cold unsalted butter, cut into 1/2-inch pieces 
5 to 6 tablespoons ice water 

For the filling:

5 tablespoons butter 
1 medium yellow onion, diced small
1 stalk celery, diced small  
2 medium carrots, diced small 
1 medium russet potato, peeled, diced small 
6 tablespoons all-purpose flour 
1/2 teaspoon dry thyme
1/2 teaspoon dry tarragon
3 cups chicken broth 
1 cup frozen peas, thawed 
Salt and white pepper 
3 cups cooked chicken, diced 

1. For the crust: In a food processor, pulse together flour and salt. Add cold butter and pulse until mixture resembles coarse meal, with a few pea-size pieces of butter remaining. Sprinkle with 5 tablespoons ice water. Pulse until dough is crumbly but holds together when squeezed, adding 1-2 more tablespoons ice water as needed; don’t overmix.
2. Dump the dough onto a piece of plastic wrap and shape it into a smooth disk; refrigerate for 30 minutes – 1 hour. (You could make this the day before.)  
3. For the filling: In a large pot, melt butter over medium-high heat. Add onion, carrots, celery, and potatoes and season with salt. Cook until softened, about 8 minutes, stirring often. Stir in the flour and herbs.
4. Drizzle in the broth while stirring. Bring to a boil, reduce heat, and simmer until thickened, about 8 minutes, stirring occasionally. Stir in the peas and chicken. Season generously with salt and pepper. Cook another 5 minutes. Pour filling into a 2-quart baking dish. Let cool.
5. Heat oven to 375°F. On a work surface dusted with flour, roll out the dough so it’s about an inch wider than the dish. Place dough over the cooled filling and fold the extra dough under itself, pressing down. Poke a few vents in the dough. Place dish on a rimmed baking sheet and bake until crust is golden brown and filling is bubbling, 50 – 60 minutes. Let cool 10 minutes before serving.