Mile-High Chicken Potpie

Directions

1. In a small bowl, beat egg yolk with 2 tablespoons water. In a large bowl, combine flour and salt; cut in butter until crumbly. Gradually add yolk mixture, tossing with a fork; add additional water 1 tablespoon at a time, as needed, until dough forms a ball. Divide dough into 2 portions, 1 with three-quarters of the dough and 1 with the remainder. Shape each into a disk; cover and refrigerate 1 hour or overnight.
2. For filling, in a Dutch oven, melt butter. Saute potatoes, carrots, celery and onion until crisp-tender, 5-7 minutes. Stir in flour, bouillon, tarragon and pepper. Gradually stir in cream. Bring to a boil; cook and stir until thickened, about 2 minutes. Stir in chicken and peas; set aside to cool completely.
3. On a lightly floured surface, roll out larger portion of dough to fit bottom and up the side of an 8-in. springform pan. Place dough in pan; add cooled filling. Roll remaining dough to fit over the top. Place over filling. Trim, seal and flute edge. Cut slits in top. Chill for at least 1 hour.
4. Lightly beat egg white with 1 teaspoon water. Brush over the top crust; sprinkle with celery seed. Place pie on a rimmed baking tray.
5. Bake at 400° until crust is golden brown and filling is bubbly, 50-55 minutes. Cool on a wire rack for at least 30 minutes before serving.