Rhubarb Custard Pie

This is the pie we want to make the moment that fresh spring rhubarb is available. The pink hue from the rhubarb is stunning against the silky custard. 

Rhubarb Custard Pie
4 cups (400 g) rhubarb, 1" pieces
1/2 cup (100 g) sugar
4 tbsp (27 g) cornstarch
1/2 cup (100 g) sugar 
1/4 tsp salt
60 ml heavy cream
3/4 cup (180 g) sour cream
1/8 tsp freshly grated nutmeg and more for garnish
1/2 tsp vanilla
2 eggs
1 recipe for Sifted Spelt Pastry Dough
1 egg white 

Pre-Bake Pie Dough
Remove pie dough from the fridge. Lightly flour a rolling pin and roll one disc into a circle about 13 inches wide and approximately 1⁄8-1/4" thick. Gently ease the dough into a 9-inch pie pan, lightly pressing it into the contours of the pan and making sure there is about 1/2-1 inch over hang all around. If any part tears or comes away, simply press the dough back together. Fold the edges over and crimp into a decorative pattern with your fingers or a fork. Place in freezer until frozen solid, about 30 minutes. 

Preheat oven to 400°F and place a baking sheet in the oven to heat up. 

Remove pie shell from the freezer and line it tightly with two pieces of aluminum foil (shiny side down, one piece going horizontally and the second vertically). Press the foil tightly into the bottom and edges of the pie pan. Pour pie weights (dry beans, rice or sugar also work well) onto the aluminum foil and fill until close to the top. Place pie pan on the pre-heated baking sheet (don't forget the pan will be very hot!) and bake for approximately 30-45 minutes, until the pastry dough is set and almost dry to the touch. If the dough looks soft or gooey, continue baking for 5 more minutes before checking again. 

Remove the foil and pie weights and return crust to the oven to bake for an additional 5-10 minutes. If the bottom of the crust has puffed, prick with the tines of a fork to allow stems to escape. Set aside to cool for a few minutes. Turn oven down to 350°F and make the egg wash.

To make an egg wash, lightly whip up the egg white with 15ml water with a fork. Using a pastry brush, brush the bottom and sides of the pie dough with egg wash, this helps to protect the dough from becoming soggy. Place crust in the oven and bake for 5 minutes to set the seal. Set pre-baked pie shell on a cooling rack while the filling is being prepared. 

Assemble Filling and Bake 
Place cut rhubarb into a large pot and add sugar and cornstarch. Cook over medium-low heat and stir frequently with a rubber spatula, ensuring that the edges of the pot are well scraped. Continue stirring for 10-15 minutes as the juices release and the mixture starts to thicken. Once the mixture starts to bubble, stir constantly for 1 minute to cook out the flavour of the cornstarch. 
Remove rhubarb from heat and allow to cool. Once cooled, pour the rhubarb filling into the bottom of the pre-baked single crust pie shell and place in refrigerator while the custard is being prepared. 

Preheat oven to 350°F.

In a large bowl, whisk together sugar, salt, heavy cream and sour cream. Stir in the nutmeg and vanilla. Add eggs one at a time and whisk until smooth and homogenous.

Place pie on a baking tray. Using a fine mesh sieve, strain the custard directly onto top of the rhubarb filling and place in oven. Bake for 35-45 minutes, rotating the tray half way, until the edges of the filling are set, slightly puffed and the centre has a slight wobble. The colour should be light golden. The filling will continue to cook and firm up after the pie is removed from the oven. 

Allow pie to cool for 2-3 hours before garnishing the top with freshly grated nutmeg and slicing. Pie can be eaten warm, room temperature or cool.