With a pie cutter, cut in the shortening until the particles are like course sand.
Sprinkle in water, 1 tsp or so at a time, mixing lightly with a fork.
Press the dough into a ball.
Roll the crust out on a piece of parchment paper (the dough should be about a ⅛ of an inch thick), making the crust roughly the shape of a circle.
Place the pie crust onto a cookie sheet lined with parchment paper.
Rhubarb Filling:
In a bowl combine the rhubarb, sugar, salt and cornstarch.
Let rest for about 10 minutes, then mix well.
Putting it all together:
Place the rhubarb filling into the centre of the pie dough sheet.
Fold the edges of the pastry over to cover the outer edge of the rhubarb pile. Overlap as needed.
Brush the pastry with milk, then generously sprinkle on some sugar (I like to use a cinnamon/sugar mix).
Place the galette into the oven, then immediately TURN DOWN the heat to 350 degrees.
Bake for 1 hour and 15 minutes, or until the pastry is golden brown.
When the galette is done baking, remove it from the oven and brush the rhubarb centre with the jelly glaze. Let the galette sit for about 10 minutes before serving.
Serve slightly warm with ice cream or whipping cream!