Blueberry Rhubarb Pie

I tried this dish recently. It's really just the right amount of sweet and the crust is flaky and delicious.

For The Crust:

2 cups flour
10 tbsp (1 stick plus 2 tbsp) butter, chilled and cut into bits
1/2 tsp salt
1/2 tsp baking powder
1/2 cup sugar
1/3 cup cold milk

For The Filling:

2 tbsp cornstarch
1/3 cup water
1 pound thin to medium rhubarb stalks (about 5), cut into 1" pieces
1/2 cup plus 2 tbsp. sugar
1/2 tsp finely grated lemon zest
1/2 tsp ground cinnamon
1/8 tsp salt
1 1/2 cup fresh blueberries
2 tbsp butter
1 egg, beaten

To make the crust: In a bowl of a food processor or in a large bowl, combine the flour, butter, salt and baking powder, and sugar and process 10 to 12 seconds, or mash with your fingertips, until the mixture has the dry, crumbly texture of coarse cornmeal. Add the milk and pulse 10 to 12 times, or work together with your fingertips, just until the dough comes together in a smooth mass, but before it forms into a ball. If the dough is too dry, add another tbsp of milk and pulse or mix for another few seconds. Remove the dough from the bowl and work it into a ball with your hands. If the dough is very sticky, coat your palms with flour once or twice and work into the dough. The dough should be malleable but should not stick to your hands. Divide the dough in half and transfer onto 2 pieces of waxed paper, press the dough into flat disks, wrap well and refrigerate for at least 1 hour.

To make the filling: In a medium saucepan, combine the cornstarch with the water and stir to dissolve. Add the rhubarb, 1/2 cup of the sugar, the lemon zest, cinnamon, and salt and cook over medium-high heat, stirring frequently, for 3 minutes. Remove from heat, cool for 5 minutes, then add the blueberries and stir to combine. Set aside.

Preheat the oven to 425. Lightly butter a 10 1/2 " tart pan. On a floured work surface, roll out the dough with a floured rolling pin into two 13" circles. Transfer one circle to the tart pan and press the dough gently into the bottom and sides. Fold the overhang over onto itself so that just 1/2 " extends over the rim. Flute the edges between your thumb and forefinger, or gently crimp with the tines of a fork. Using a cookie cutter in the shape of your choice, cut shapes from the remaining circle of dough. Spoon the filling into the pie crust and dot with the butter. Arrange the cut-out dough over the top of the filling, with the pieces touching but not overlapping. Brush the rim of the bottom crust and the cut-out dough on top with the egg and sprinkle with the remaining 2 tbsp sugar.

Bake in the center of the oven for about 40 minutes, until the crust is golden brown.

Set aside on a wire rack to cool.

(I used twice as much filling and filled up a deep dish pie pan. It was really good!)