For the Pie

• In a food processor, pulse the flour and salt. Add the chilled butter and pulse until it is the size of small peas. Add the frozen butter and pulse until it is the size of small peas.
• Mix the vinegar and ice water together and drizzle over the flour mixture. Pulse just until the dough starts to come together.
• Turn out on a lightly floured surface and press together to form a smooth dough. Divide the dough in half and flatten into two disks. Wrap in plastic wrap and refrigerate until firm, at least 2 hours, or freeze 30 minutes.
• On a lightly floured surface, roll one disk of pastry into a 12-inch circle, 1/8-inch thick. Transfer the rolled-out pastry into a 9-inch or 10-inch pie plate and freeze for 20 minutes. Roll out the remaining pastry 1/8-inch thick. Transfer to a baking sheet and freeze 20 minutes.
• For filling: In small bowl, whisk 1 cup sugar, tapioca and salt. In a medium bowl, toss the cherries, raspberries and blueberries together. Sprinkle with the sugar mixture and toss gently.
• Mix together 1 teaspoon flour and the remaining 1 teaspoon sugar. Sprinkle in the crust; tap or brush out the excess. Spoon the filling into the crust.
• Top pie with second crust. Press the edges together with your fingers and flute or use a fork to seal. Cut slits or decorative designs in several places in top crust. Freeze the pie for 1 hour.
• Preheat oven to 400°F. Brush the top crust with cream and sprinkle with sugar.
• Bake pie in the middle of the oven for about 1 hour, until the crust is richly browned and the filling starts to bubble. If necessary, cover the pie with foil to prevent overbrowning the last 10 minutes of baking. Let the pie cool for at least 4 hours before slicing.