This classic Rhubarb Custard Pie is one of my family all time favorites. Pure rhubarb fans will love the sweet and tart flavors in this rhubarb dessert.
In a large bowl, toss together rhubarb, ⅓ cup of flour, white sugar, and cinnamon until rhubarb is coated. Stir in beaten egg until combined. Set aside.
Place flour, salt, and sugar in food processor. Pulse a couple of times to combine. Place shortening and butter in food processor on top of flour mixture. Pulse flour crumbles start to form. Do not over pulse.
Add the ice water a little at a time, pulsing food processor a couple of times after each addition. Once dough begins to form into a ball remove from food processor and place on a lightly floured surface.
Knead dough together to form a ball being careful not to handle dough too much. Divide pie dough into two pieces and flatten each piece of dough into a round disk.
Roll dough out on a floured surface until about 10-11 inch circle in diameter. Place bottom crust in pie pan and fit to pie dish.
Transfer rhubarb mixture to the bottom crust in the pie dish. Dot the top of the pie with butter.
Using cold water, dab fingers into the water and then lightly tap the edge of the bottom pie dough with your fingers to dampen the dough.Roll out second disk of dough, fold the dough in quarters (it will be triangle shape), and cut 2-3 slits on each side of the triangle and place on ¼ of the pie.
Unfold dough and carefully transfer dough to cover top of pie. Gently pick up folded half and bring to cover the pie. Pinch edges of pie together removing any excess dough around the edges of the pie. Crimp pie dough together as desired.
Cover pie with pie guard or aluminum foil and bake for 25 minutes. Remove guard/foil and continue baking for another 30 minutes until filling is bubbly and pastry is golden brown.
Remove from oven and cool completely before cutting.