How to Make It
Prepare the Crust: Whisk together flour and salt in a medium bowl. Add cold cubed butter, and use your fingers to quickly work butter into flour mixture. (Some butter pieces will be the size of oat flakes, and some will be the size of peas.) Create a well in flour mixture, and pour in cold buttermilk. Use a fork to bring dough together, moistening all flour bits. Dump dough mixture onto a lightly floured work surface. Dough will be moist and shaggy. Divide dough in 2 pieces, and gently knead each piece into a disk. Wrap each disk in plastic wrap, and chill 1 hour.
Meanwhile, prepare the Filling: Melt 4 tablespoons of the butter in a large saucepan over medium. Whisk in flour, and cook, whisking constantly, about 1 minute (mixture will be very thick). Reduce heat to low; gradually add chicken stock, whisking constantly until no flour bits remain. Whisk in milk. Increase heat to medium-low; cook, whisking often, until mixture is consistency of thick pudding, about 20 minutes. Remove from heat, and whisk in salt and pepper; set aside.
Melt remaining 2 tablespoons butter in a large skillet over medium. Add onion; cook, stirring constantly, until translucent, about 3 minutes. Add garlic; cook, stirring constantly, 1 minute. Add carrots and green beans; cook, stirring occasionally, 5 minutes (vegetables will not be cooked through). Stir in peas, thyme, and sage; cook 1 minute. Remove from heat, and stir in turkey. Stir turkey-vegetable mixture into stock mixture in saucepan; cool slightly, about 5 minutes.
Prepare the Topping: Bring water and butter to a boil in a large saucepan over medium, stirring occasionally to melt butter. Add stuffing mix, and gently stir to combine. Cover and remove from heat. Let stand 10 minutes.
Remove 1 pie dough disk from refrigerator. Unwrap and roll dough into a 1⁄4-inch-thick round on a lightly floured surface. Cut an 8-inch circle from a piece of parchment paper. Use parchment round as a guide to cut 8-inch rounds from piecrust using a sharp knife. Fit 1 piecrust round in bottom and up sides of each skillet. Repeat with remaining dough disk, rerolling scraps as needed, until all 8 skillets are lined.
Preheat oven to 375°F, and place racks in lower and upper third of oven. Spoon about 1 1⁄2 cups Filling into each Crust; cover with about 3⁄4 cup Topping. Bake in preheated oven until Crust is golden brown and Filling is lightly bubbling, 45 to 50 minutes, rotating skillets halfway through baking. Remove from oven, and let stand 20 minutes before serving.