- PASTRY: Stir together flour, sugar and salt in a large bowl. Using a pastry blender or your hands, cut in butter until coarse crumbs form. Using a fork, stir in ice water to create a soft dough that can easily be formed into a ball. Add more ice water, 1 tbsp at a time, if needed. Dough should not be sticky. Divide dough, forming into 2 discs. Wrap with plastic wrap and refrigerate until cold, at least 45 min or overnight.
- COMBINE rhubarb and strawberries in a large bowl. When you’re ready to roll out pastry and assemble pie, stir sugar, tapioca and zest into fruit. Let stand, stirring occasionally, for 15 min, so that berries and rhubarb release juices.
- PLACE rack in lowest position in oven. Preheat oven to 425F. Using a floured rolling pin, roll one disc of pastry on a floured surface into a 12-in. circle. Loosely roll up around rolling pin. Unroll over 9-in. deep-dish pie plate. Press dough over bottom and sides of pie plate. Don’t prick. Trim pastry, leaving a 1/4-in. overhang. Roll out remaining pastry disc into an 11-in. circle.
- SPREAD filling evenly into pie crust. Moisten edge of bottom crust with water. Roll top crust around rolling pin, then unroll over filling. Trim edges, leaving 1-in. overhang.
- FOLD top edge under bottom edge. Crimp edges together using your index finger and thumb. Or press around edges using the tines of a fork.
- LIGHTLY brush top crust with egg. Cut small slits or a round hole in top crust for steam to escape. Sprinkle with sugar. Place pie on a baking sheet.
- BAKE on bottom rack for 15 min. Reduce temperature to 350F. Continue baking until bottom and top crusts are golden and fruit is bubbling, 45 to 60 min. Cool completely on a rack, at least 2 hours, before slicing. Cut into wedges.
If making pastry in the food processor: Whirl flour, sugar and salt to mix. Add butter, then pulse until crumbs form. While motor is running, pour ice water and lemon juice through spout. Continue whirling just until dough comes together. Add more ice water, 1 tbsp at a time, if needed. Dough should not be sticky. Divide and refrigerate, 45 minutes to overnight.
Let chilled pie dough stand at room temperature for a few minutes before rolling out. This will help prevent tears in the pastry.
We worked hard to get this fruit filling just right – not too runny or too thick. We even made versions with different amounts of tapioca and asked our co-workers to pick their favourites. And the last key to a luscious texture? Waiting for the pie to cool before digging in!