1-2pats of salted butter to top the filling before placing top crust on pie
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 well floured surface (such as a pastry mat). Bring dough together to form a ball being careful not to handle dough too much. Divide dough into two pieces and flatten out into a circle. Roll dough out on a floured surface until about 10-11 inch circle in diameter. Place 1 circle in bottom of pie pan and form to shape. Place other disc of dough in refrigerator until ready to top the pie.
Pre-heat oven to 375 degrees. Toss together rhubarb, flour, sugar, and cinnamon until rhubarb is coated. Stir in beaten egg until combined. Place filling in well of pie crust in your pie pan.
Roll out 2nd disc of dough, fold in half and cut slits in center of dough. 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 edged as desired. Brush top of dough with non-fat milk and sprinkle with sugar 1 tablespoon of sugar.
Cover pie with pie guard or aluminum foil and bake for 25 minutes. Remove guard/foil and continue baking for another 20-30 minutes until filling is bubbly and pastry is golden. Remove from oven and cool completely before cutting. Store leftovers in a cool, dry place.