To make the dough, place the flour, sugar and salt into a food processor fitted with a blade attachment. Pulse for a few seconds to combine. Pour 6 tablespoons of cold water over a few ice cubes. Let sit for a few seconds to chill. Remove the ice cubes from the chilled water, and add the butter and water to the flour mixture.
Pulse until the mixture forms a rough dough. Turn out onto a lightly floured surface and knead the dough. Form into a square, wrap in plastic wrap and refrigerate for at least 10 minutes.
For the filling:
Heat a large pot over medium heat, add the olive oil and heat through. Add the onion, celery and potato and sauté until tender and opaque, about 6 minutes.
Add the turkey and cook until the meat is browned all over and the potatoes are soft, about 6 to 8 minutes. Season with salt and pepper then stir in the flour. Add the chicken stock and bring to a simmer, until the sauce thickens, about 4 minutes. Fold in the cheese, cranberry sauce, and chives.
For assembly:
Preheat oven to 400ºF (200ºC).
Remove the dough from the refrigerator, unwrap and roll out on a lightly floured surface so the dough is about ¼” thick. Cut the dough into 4” squares, gathering the dough and re-rolling as needed. Press the dough into a lightly oiled standard size muffin tin and scoop about 2 rounded tablespoons of the turkey filling mixture into each tin.
Cover each with second piece of dough, and use a fork to seal the edges together. Brush the beaten egg over the top of each mini pot pie. Bake until the crust is golden brown, about 20 to 25 minutes. Serve hot or at room temperature.