Tourtière (Québécois Meat Pie)

Whisk together flour, mustard, zest, and salt in bowl; add butter, and using your fingers, rub mixture until pea-size crumbles form. Add juice and 7 tbsp. ice-cold water, and stir with a fork until dough just comes together. Transfer to a work surface, and form into a ball; halve, and form each half into a disk. Wrap disks in plastic wrap and refrigerate for 1 hour.

Meanwhile, bring a 4-qt. saucepan of water to a boil; add potatoes, and cook until tender, about 6 minutes. Drain, and mash until smooth; set aside. Heat oil in a 4-qt. saucepan over medium-high heat. Add pork, and cook, stirring, until no longer pink, about 4 minutes. Add garlic, onions, and carrot, and cook, stirring, until soft and pork is well browned, about 20 minutes. Add cider, celery seed, cloves, nutmeg, cinnamon, ginger, bay leaves, and pepper, and cook until all liquid is evaporated, about 3 minutes. Remove from heat, and stir in mashed potatoes; let filling cool completely.

Heat oven to 400°. Place 1 dough disk on a lightly floured work surface, and using a rolling pin, roll until ¼" thick. Transfer to a 9" pie dish, and let excess hang over edge; pour filling into pie dish, and smooth top. Roll remaining dough disk until ¼" thick, and place over filling. Trim dough sheets to within 1" of edge of pie dish, fold edge underneath itself, and crimp with your fingers or a fork, if you like. Brush with egg wash, and using a paring knife, cut four 2" slits in the top of the pie. Bake until pastry is golden brown and filling is heated through, about 50 minutes.