Combine 3 pounds apples (diced) with 4 oz brown sugar, 4 oz apple cider, 2 oz Bourbon, ⅛ teaspoon salt and 1 teaspoon ground cinnamon. Split ½ vanilla bean and scrape out the seeds. Add the seeds and bean pod to the apples. Set aside to macerate for at least 1 hour and as long as 3 hours. (See Note)
Drain the apples, saving the juice. Combine ¼ cup of the juice with 2 tablespoons cornstarch. Set aside
Put the apples and the rest of the juice in a large saucepan. Cook over medium-high until the juices begin to boil. Reduce the heat to medium-low and continue cooking until the apples are crisp-tender, stirring often. The apples should still hold their shape. The exact time will depend on the type of apple, estimate 10 minutes.
Add the corn starch mixture to the apples. Increase the heat to medium-high and return to a boil, stirring constantly. Cook until the juices are slightly thickened and become translucent. Transfer the apple filling to a container and cool to room temperature. Chill until ready to use. The filling can be made 2-3 days ahead.
Preheat the oven to 350 °F. Place six 1-cup ramekins or a large casserole dish onto a sheet pan. Divide the apple filling between the dishes (or pour into the casserole dish).
Roll the puff pastry to a 1/4" thick. For individual pies use a biscuit cutter to cut six 4½" circles. For a large pot pie use the entire sheet.
Brush the edges of the ramekins with egg wash. Place a dough round onto each dish and fold the edges over. (see note) Make a slit into the top of each small pie or a large "x" if making one larger pie. Brush the tops of the pies with egg wash and sprinkle with granulated sugar.
Bake until the pastry is puffed and lightly browned, about 20 minutes. Serve warm.