We used a mix of heirloom apples ( available at farmers' markets, orchards, and by mail-order), but feel free to substitute any firm, tart cooking apples.
On a lightly floured surface, roll 1 disk of pate brisee to 1/8-inch thickness. Fit into a 9-inch deep-dish pie plate. Trim edges, leaving a 1-inch overhang. Freeze until firm, about 15 minutes. Roll remaining disk of dough into a 12-inch circle, about 1/8-inch thick. Transfer to a parchment-lined baking sheet, and freeze until cold and firm, about 15 minutes.
Peel and core apples, then cut them into 1/2- to 1-inch chunks and place in a medium bowl. Add flour, granulated sugar, lemon juice, salt, cinnamon, and vanilla seeds, and toss.
Place apple mixture in prepared pie dish, and dot with butter. Center dough round over apples, and tuck overhang under edge of bottom dough. Using your fingers, gently pinch dough along edge to seal. Using a paring knife, cut eight 2 1/2-inch vents in dough to let steam escape. Freeze pie until firm, about 2 hours.
Preheat oven to 425 degrees. Mix yolk and cream in a small bowl, and gently brush over dough. Sprinkle with sanding sugar. Place dish on a rimmed baking sheet, and bake for 15 minutes. Reduce heat to 375 degrees, and bake until crust is golden brown and juices are bubbling, 60 to 75 minutes. Transfer pie to a wire rack, and let cool.
The filling will be liquidy when it comes out of the oven. Let stand overnight, uncovered, so the apples absorb the juices.