Combining tart rhubarb with sweet strawberries, this pie avoids any liquidy and oozing filling by using both flour and cornstarch as thickeners. Some of the filling is also pre-cooked to further curb the moisture, ensuring a crisp-bottomed and perfect pie every time.
1tbspdemerara sugar or granulated sugar, for sprinkling over the pie
Instructions
Add the caster (or granulated) sugar and lemon zest to a large mixing bowl. Use your fingertips to massage the zest into the sugar until it resembles wet sand. Add the rhubarb and strawberries and lemon juice and stir to coat in the sugar. Let rest at room temperature for 30 minutes.
Lightly flour a work surface and, using a rolling pin, roll the dough until it's roughly 5mm (⅛in) thick and 30cm (12in). Cut the dough into 4cm (1½in) strips, transfer to a baking tray and refrigerate. Roll out the other portion to the same specifications and transfer to a 23cm (9in) pie plate. Refrigerate.
After 30 minutes, set a fine mesh sieve over a medium saucepan and drain the liquid from the fruit. Set the fruit aside and put the pan over medium-low heat. Cook until the syrup is thick and reduced by half - 2-3 minutes. Add the butter and once melted, whisk in the flour. Cook for another minute or two.
Preheat oven to 200°C/400°F. Add ⅔ of the fruit to the saucepan and stir to coat in the syrup and flour roux. Cook the fruit, stirring frequently, until it releases a lot of its moisture and the strawberries have begun to break down - about 10 minutes.
Add the cooked fruit to the rest of the uncooked fruit along with the brown sugar, cornstarch and vanilla paste. Remove the pie dish and pastry from the refrigerator and scrape the filling into the dish, ensuring it's evenly distributed.
Remove the strips of pie dough from the fridge. Vertically arrange half of the strips - evenly spaced - parallel across the top of the pie with the longest strip in the middle and the shortest strips on the edges. Fold back every other strip of dough and lay one strip perpendicular across the vertical strips.
Unfold the strips so that they lay over the piece of dough placed down. Fold up the alternating strips of dough and lay another horizontal dough strip on top. Repeat until the top of the pie is covered.
Trim the dough from the edges of the pie ensuring that there is a 1cm (½in) overhand over the edge of the pie dish. Fold the excess over itself to make a clean edge and the crimp to seal. Move the pie to a rimmed baking sheet and put in the freezer for 10 minutes.
Remove the pie from the freezer and brush the pie dough with the beaten egg and then sprinkle with sugar. Move to the oven and immediately lower the temperature to 180°C/350°F.
Bake until the crust is crisp golden and the filling is bubbling through the gaps in the lattice - about 1 hour to 1 hour 15 minutes. Allow the pie to cool completely before slicing and serving, at least 4 hours.