Black and Blue (Berry) Pie

INGREDIENTS

• 455 g (3 cups + 3 tablespoons) all purpose flour
• 300 g (1 cup + 5 tablespoons) salted butter, refrigerator cold
• 1/3 cup vodka
• 1/3 cup ice cold water
• 340 g (12 oz or 2 1/2 cups) blackberries
• 510 g (18 oz or 3 1/2 cups) blueberries
• 200 g (1 cup) granulated white sugar
• 45 g (3 tablespoons) potato starch (not potato flour)
• zest of 1 medium orange (~1 tablespoon)
• 1/4 teaspoon all spice
• 1/8 teaspoon (a generous pinch) nutmeg
• 1 large egg, separated into yolk and white for wash
• 1 to 2 tablespoons of extra sugar for sprinkling on top