1/4 cup (60 mL) ice water
1 tbsp (15 mL) apple cider vinegar
1 1/4 cups (310 mL) all-purpose flour, 165 g
1/2 tsp (2 mL) sugar
1/4 tsp (1 mL) fine sea salt
1/2 cup (125 mL) unsalted butter, cold, cut into cubes
1 egg white, lightly beaten
Topping
2/3 cup (150 mL) all-purpose flour
1/3 cup (80 mL) skinned hazelnuts, coarsely chopped
1/4 cup (60 mL) old-fashioned rolled oats
1/4 cup (60 mL) packed light brown sugar
2 tbsp (30 mL) sugar
1/4 tsp (1 mL) fine sea salt
1 1/2 tsp (7 mL) ground cardamom
1/3 cup (80 mL) unsalted butter, melted, cooled
Filling
7 cups (1.75 L) raspberries, about 840 g
1 tbsp (15 mL) fresh lemon juice
1/4 cup (60 mL) sugar
Pinch salt
1/4 cup (60 mL) tapioca starch
Directions For the pastry, combine water and vinegar in a liquid measuring cup and add a few ice cubes. Keep in the fridge until ready to use.
Combine flour, sugar and salt in a medium bowl. Add butter and work with your fingers, pressing all the butter cubes flat until they are incorporated into the flour as large and small pieces. Drizzle in enough ice water mixture, stirring with a fork to start then with your fingers, to just bring dough together into a ball—do not overwork! Wrap dough in plastic and flatten into a disc. Refrigerate at least 30 minutes and up to 3 days.
For the topping, combine flour, hazelnuts, oats, sugars, salt and cardamom in a medium bowl. Drizzle in butter and stir with a fork until absorbed into dry ingredients. Cover and refrigerate until you can easily break crumble up into small and large clumps, at least 30 minutes.
Place rack in lower third of oven. Preheat to 425°F (218°C).
Remove pastry from fridge and allow it to warm up enough to be pliable (up to 10 minutes). Roll out on a floured surface until it’s large enough to fit into a 9-inch (23-cm) pie plate with a 1-inch (2.5‑cm) overhang. Trim pastry as needed, roll edge under and crimp as desired. Place in freezer until solid (about 15 minutes).
Dock pastry all over with a fork. Line with parchment and weigh down with pastry weights or dried beans. Bake in lower third of oven until edges are lightly golden, about 18 minutes. Remove parchment and weights. Bake until bottom is set, 3 to 5 minutes more. Use a fork to compress any bubbles that may have formed. Remove from oven, wait 3 minutes then brush warm crust with egg white to seal. Cool completely before filling.
Reduce oven to 375°F (191°C) and place a rimmed baking sheet lined with foil in bottom third of oven.
For the filling, combine raspberries, lemon juice, sugar and salt in a large mixing bowl. Toss gently to combine. Let stand until sugar has dissolved and berries are evenly juicy, about 30 minutes. Strain juices into a small saucepan and bring to a boil over medium-low heat. Simmer until thickened and reduced to no more than 1/4 cup (60 mL). Set aside. Add tapioca to raspberries and gently toss to combine. Set aside.
Transfer raspberries to crust and drizzle reduced juices overtop. Sprinkle with topping. Place on preheated baking sheet and bake until crumble is deeply golden, about 45 minutes. Cover loosely with foil and continue baking until raspberry juices are bubbling, 20 to 30 minutes more. Remove from oven and transfer to a cooling rack. Cool completely, ideally overnight, to set before serving. Serves 8
