This savory, double-crusted pie is delicious served warm or chilled.
In a large skillet over medium-high heat, cook bacon until fat begins to render, about 2 minutes. Add ground pork and cook, breaking it up into bite-size pieces, until no longer pink, 5 to 7 minutes. Transfer to a plate. Return skillet to medium-high; swirl in oil. Add onion, garlic, and celery; season with salt. Cook, stirring occasionally, until softened and brown in spots, 7 to 9 minutes. Return pork mixture and any accumulated juices to skillet. Stir in potato, broth, cinnamon, and clove; season with pepper. Reduce heat to medium and simmer, stirring occasionally, until broth is mostly evaporated, 25 to 28 minutes.
Transfer pork mixture to a bowl and let cool to room temperature, about 30 minutes. Lightly beat 1 egg; stir into pork mixture with parsley.
Preheat oven to 400 degrees with racks in center and lowest positions. Roll out one disk of dough to an 11-inch round on a work surface dusted with flour. Transfer to a 9-inch pie plate; trim edges to a 1/2-inch overhang. Transfer pork mixture to pie shell. Roll remaining dough to an 11-inch round and center over filling. Trim edges to a 1/2-inch overhang. Fold edges of top crust under edges of bottom crust, tucking dough until flush with edge of pie plate. Crimp edges with the tines of a fork. Freeze until firm, about 20 minutes. Beat remaining egg with 1 teaspoon water. Brush crust with egg wash, then cut a few vents in top of crust.
Bake the chilled pie on the center rack with a rimmed baking sheet on the lowest rack (to catch any drips) until crust is golden brown and filling bubbles slightly through vents, 50 minutes to 1 hour. Let cool on a wire rack 30 minutes before slicing. Serve with mustard and cornichons.