In a food processor add flour, sugar, salt, and cinnamon, pulse 3 times to combine.

Add butter and pulse until mixture resembles coarse cornmeal with a few pea-size pieces of butter remaining.

Drizzle in water until dough ball forms (add another tablespoonful of water if needed).

Transfer dough to a ball and cover tightly with plastic wrap and chill for at least 45 minutes.

Preheat oven to 400°F.

In a large bowl mix apples, brown sugar, salt, cinnamon, nutmeg, ginger, lemon juice, and rum let sit for 10 minutes.

Roll out dough on a lightly floured surface to a 12" round.

Transfer to a parchment-lined baking sheet.

Layer apples in the center, leaving a 2" border.

Fold edges over, overlapping slightly.

Brush dough with beaten egg and sprinkle with sugar.

Bake galette for 40-45 minutes, until crust is golden brown.

Cool for 5 minutes before serving with a scoop of ice cream.